feat: implement Phase 1 payment gateway, real-time SignalR, kitchen-inventory deduction, and order payment flow

- wallet-service: IPaymentGateway abstraction + VN Pay implementation (HMAC-SHA512, sandbox), Payment aggregate root, PaymentsController with create/callback/query endpoints - order-service: PosHub SignalR hub with Redis backplane + MessagePack, strongly-typed clients, 3 group types (shop/kds/pos), integrated into Create/Pay/Complete/Cancel order handlers - fnb-engine + inventory-service: Kitchen→Inventory auto-deduction via domain events, HTTP with Polly retry + circuit breaker, idempotency check, graceful degradation on insufficient stock - order-service: Enhanced PayOrderCommand with 3 flows (cash/card/online), PaymentPending status, WalletServiceClient, CompleteOrderPaymentCommand for gateway callbacks - POS frontend: Cash/Card/QR payment components wired to real backend, BFF proxy updated - infra: Traefik routes for fnb-engine, inventory-service, and SignalR WebSocket hub - ROADMAP.md: Updated with Phase 1 progress tracking Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
2026-03-06 13:28:46 +07:00
parent 5d9a41fde9
commit 8af86e9e89
78 changed files with 4047 additions and 81 deletions
--- a/ROADMAP.md
+++ b/ROADMAP.md
@@ -91,12 +91,12 @@

 | # | Gap | Status | Owner | Sprint | Notes |
 |:-:|-----|:------:|-------|:------:|-------|
-| 1 | Payment Gateway — VN Pay | `TODO` | Backend #1 | Phase 1 / W1-2 | wallet-service integration |
+| 1 | Payment Gateway — VN Pay | `DONE` | Backend #1 | Phase 1 / W1-2 | wallet-service: IPaymentGateway + VnPayGateway |
 | 2 | Payment Gateway — Momo | `TODO` | Backend #2 | Phase 1 / W1-2 | wallet-service integration |
-| 3 | Real-time SignalR Hub | `TODO` | Backend #3 | Phase 1 / W1-2 | KDS + order push updates |
-| 4 | Kitchen → Inventory Deduction | `TODO` | Backend #1 | Phase 1 / W2 | fnb-engine → inventory-service |
+| 3 | Real-time SignalR Hub | `DONE` | Backend #3 | Phase 1 / W1-2 | PosHub + Redis backplane + MessagePack |
+| 4 | Kitchen → Inventory Deduction | `DONE` | Backend #1 | Phase 1 / W2 | Domain events + HTTP + Polly + idempotency |
 | 5 | Multi-tenant Row-Level Security | `TODO` | Backend #2 | Phase 1 / W2-3 | All services, DB level |
-| 6 | Payment UI Completion | `TODO` | Frontend Blazor | Phase 1 / W1-2 | Connect to real gateway |
+| 6 | Payment UI Completion | `DONE` | Frontend Blazor | Phase 1 / W1-2 | Cash/Card/QR wired to real gateway |
 | 7 | Integration Test Suite | `TODO` | QA Engineer | Phase 1 / W3 | Order lifecycle e2e |
 | 8 | Staging Deployment | `TODO` | DevOps | Phase 1 / W3-4 | K8s + monitoring |

@@ -133,18 +133,18 @@

 | Task | Agent | Status | Depends On |
 |------|-------|:------:|:----------:|
-| VN Pay payment gateway integration | Senior Backend #1 | `TODO` | wallet-service |
+| VN Pay payment gateway integration | Senior Backend #1 | `DONE` | wallet-service |
 | Momo payment gateway integration | Senior Backend #2 | `TODO` | wallet-service |
-| SignalR hub for real-time updates | Senior Backend #3 | `TODO` | — |
-| KDS push notifications via SignalR | Senior Backend #3 | `TODO` | SignalR hub |
-| Payment UI — connect to real gateway | Senior Frontend | `TODO` | Payment backends |
-| Order status push to POS | Senior Backend #3 | `TODO` | SignalR hub |
+| SignalR hub for real-time updates | Senior Backend #3 | `DONE` | — |
+| KDS push notifications via SignalR | Senior Backend #3 | `DONE` | SignalR hub |
+| Payment UI — connect to real gateway | Senior Frontend | `DONE` | Payment backends |
+| Order status push to POS | Senior Backend #3 | `DONE` | SignalR hub |

 #### Week 2-3: Data Integrity & Security

 | Task | Agent | Status | Depends On |
 |------|-------|:------:|:----------:|
-| Kitchen → Inventory auto-deduction | Senior Backend #1 | `TODO` | fnb-engine, inventory |
+| Kitchen → Inventory auto-deduction | Senior Backend #1 | `DONE` | fnb-engine, inventory |
 | Row-level security (all services) | Senior Backend #2 | `TODO` | — |
 | Rate limiting audit | DevOps | `TODO` | — |
 | Input sanitization audit | QA | `TODO` | — |
@@ -215,10 +215,14 @@

 ## VI. Recently Completed

-### 2026-03-06
+### 2026-03-06 (Phase 1 Sprint)

 | Task | Agent | Details |
 |------|-------|---------|
+| VN Pay Payment Gateway | Backend #1 | IPaymentGateway abstraction + VnPayGateway (HMAC-SHA512, sandbox), Payment aggregate, PaymentsController (4 endpoints) |
+| SignalR POS Hub | Backend #3 | PosHub (strongly-typed, 3 groups: shop/kds/pos), Redis backplane, MessagePack, 7 client methods, integrated into 4 order handlers |
+| Kitchen → Inventory Deduction | Backend #1 | KitchenTicketServedDomainEvent → HTTP call to inventory-service, Polly retry + circuit breaker, idempotency, graceful degradation |
+| Order Payment Flow | Backend #2 + Frontend | 3 payment flows (cash/card/online), PaymentPending status, WalletServiceClient, BFF proxy update, POS Cash/Card/QR components wired |
 | Account Management (Admin Settings) | Backend + Frontend | Full profile/merchant CRUD via BFF |
 | Subscription System | Backend + Frontend | Merchant entity + EF + API + dynamic UI |
 | User → Enterprise Plan | Backend + DB | hongochai10@icloud.com set to Enterprise (unlimited) |
@@ -242,6 +246,10 @@

 | Date | Decision | Rationale | Status |
 |------|----------|-----------|:------:|
+| 2026-03-06 | IPaymentGateway in Domain, implementations in Infrastructure | Multiple gateways (VNPay, Momo) via same interface | ACTIVE |
+| 2026-03-06 | PosHub in order-service (not separate service) | Order lifecycle owns real-time notifications | ACTIVE |
+| 2026-03-06 | Kitchen→Inventory via HTTP + Polly (not message queue) | Simpler, sufficient for MVP, fire-and-forget pattern | ACTIVE |
+| 2026-03-06 | 3 payment flows: cash (instant), card (instant), online (async) | Cash/card don't need gateway, only VNPay/Momo need redirect | ACTIVE |
 | 2026-03-06 | Subscription stored in Merchant aggregate | Simple, no separate service needed for MVP | ACTIVE |
 | 2026-03-06 | Static plan definitions in frontend + backend | 4 fixed tiers sufficient for MVP launch | ACTIVE |
 | 2026-03-05 | BFF pattern for frontend-backend proxy | Single entry point, auth forwarding, response normalization | ACTIVE |
--- a/apps/web-client-tpos-net/src/WebClientTpos.Client/Pages/Pos/Shared/Payment/CardPayment.razor
+++ b/apps/web-client-tpos-net/src/WebClientTpos.Client/Pages/Pos/Shared/Payment/CardPayment.razor
@@ -124,14 +124,14 @@ else
        StateHasChanged();
        try
        {
-            var success = await DataService.PayOrderAsync(_resolvedOrderId, ShopId, "card");
-            if (success)
+            var result = await DataService.PayOrderWithDetailsAsync(_resolvedOrderId, ShopId, "card");
+            if (result?.Success == true)
            {
                NavigationManager.NavigateTo($"/pos/{ShopId}/payment/success?orderId={_resolvedOrderId}&method=card");
            }
            else
            {
-                _errorMessage = "Thanh toán thẻ thất bại. Vui lòng thử lại.";
+                _errorMessage = result?.ErrorMessage ?? "Thanh toán thẻ thất bại. Vui lòng thử lại.";
            }
        }
        catch
--- a/apps/web-client-tpos-net/src/WebClientTpos.Client/Pages/Pos/Shared/Payment/CashPayment.razor
+++ b/apps/web-client-tpos-net/src/WebClientTpos.Client/Pages/Pos/Shared/Payment/CashPayment.razor
@@ -183,14 +183,16 @@ else
        StateHasChanged();
        try
        {
-            var success = await DataService.PayOrderAsync(_resolvedOrderId, ShopId, "cash");
-            if (success)
+            var result = await DataService.PayOrderWithDetailsAsync(
+                _resolvedOrderId, ShopId, "cash", amountTendered: _receivedAmount);
+            if (result?.Success == true)
            {
-                NavigationManager.NavigateTo($"/pos/{ShopId}/payment/success?orderId={_resolvedOrderId}&method=cash&change={_changeAmount}");
+                var change = result.ChangeAmount ?? _changeAmount;
+                NavigationManager.NavigateTo($"/pos/{ShopId}/payment/success?orderId={_resolvedOrderId}&method=cash&change={change}");
            }
            else
            {
-                _errorMessage = "Thanh toán thất bại. Vui lòng thử lại.";
+                _errorMessage = result?.ErrorMessage ?? "Thanh toán thất bại. Vui lòng thử lại.";
            }
        }
        catch
--- a/apps/web-client-tpos-net/src/WebClientTpos.Client/Pages/Pos/Shared/Payment/QrPayment.razor
+++ b/apps/web-client-tpos-net/src/WebClientTpos.Client/Pages/Pos/Shared/Payment/QrPayment.razor
@@ -175,14 +175,35 @@ else
        StateHasChanged();
        try
        {
-            var success = await DataService.PayOrderAsync(_resolvedOrderId, ShopId, "qr");
-            if (success)
+            // EN: Map QR provider to gateway name for online payment flow.
+            // VI: Map nhà cung cấp QR sang tên gateway cho thanh toán trực tuyến.
+            var gateway = _selectedProvider.ToLowerInvariant() switch
            {
-                NavigationManager.NavigateTo($"/pos/{ShopId}/payment/success?orderId={_resolvedOrderId}&method=qr");
+                "momo" => "momo",
+                "zalopay" => "vnpay",   // EN: ZaloPay routes through VNPay gateway / VI: ZaloPay đi qua cổng VNPay
+                _ => "qr"               // EN: VietQR — POS-confirmed, no redirect / VI: VietQR — POS xác nhận, không redirect
+            };
+
+            var returnUrl = $"{NavigationManager.BaseUri}pos/{ShopId}/payment/success?orderId={_resolvedOrderId}&method=qr";
+            var result = await DataService.PayOrderWithDetailsAsync(
+                _resolvedOrderId, ShopId, gateway, returnUrl: returnUrl);
+
+            if (result?.Success == true)
+            {
+                // EN: If payment URL returned (online gateway), redirect to payment page.
+                // VI: Nếu có URL thanh toán (cổng trực tuyến), redirect đến trang thanh toán.
+                if (!string.IsNullOrEmpty(result.PaymentUrl))
+                {
+                    NavigationManager.NavigateTo(result.PaymentUrl, forceLoad: true);
+                }
+                else
+                {
+                    NavigationManager.NavigateTo($"/pos/{ShopId}/payment/success?orderId={_resolvedOrderId}&method=qr");
+                }
            }
            else
            {
-                _errorMessage = "Thanh toán thất bại. Vui lòng thử lại.";
+                _errorMessage = result?.ErrorMessage ?? "Thanh toán thất bại. Vui lòng thử lại.";
            }
        }
        catch
--- a/apps/web-client-tpos-net/src/WebClientTpos.Client/Services/PosDataService.cs
+++ b/apps/web-client-tpos-net/src/WebClientTpos.Client/Services/PosDataService.cs
@@ -775,12 +775,50 @@ public class PosDataService

    // ═══ PAY ORDER ═══

-    public async Task<bool> PayOrderAsync(Guid orderId, Guid shopId, string? paymentMethod = null)
+    /// <summary>
+    /// EN: Payment result from order-service via BFF.
+    /// VI: Kết quả thanh toán từ order-service qua BFF.
+    /// </summary>
+    public record PayOrderResponse(bool Success, string? Status, string? PaymentUrl, decimal? ChangeAmount, string? TransactionId, string? ErrorMessage);
+
+    /// <summary>
+    /// EN: Pay an order with payment method details. Returns rich result for all payment flows.
+    /// VI: Thanh toán order với chi tiết phương thức. Trả về kết quả đầy đủ cho tất cả luồng thanh toán.
+    /// </summary>
+    public async Task<PayOrderResponse?> PayOrderWithDetailsAsync(
+        Guid orderId, Guid shopId, string paymentMethod,
+        decimal? amountTendered = null, string? returnUrl = null)
    {
        AttachToken();
-        var body = paymentMethod != null ? new { PaymentMethod = paymentMethod } : (object)new { };
+        var body = new { PaymentMethod = paymentMethod, AmountTendered = amountTendered, ReturnUrl = returnUrl };
        var resp = await _http.PostAsJsonAsync($"api/bff/orders/{orderId}/pay?shopId={shopId}", body, _writeOptions);
-        return resp.IsSuccessStatusCode;
+        if (resp.IsSuccessStatusCode)
+        {
+            // EN: BFF proxies order-service response: { success: true, data: { ... } }
+            // VI: BFF proxy response từ order-service: { success: true, data: { ... } }
+            try
+            {
+                var json = await resp.Content.ReadAsStringAsync();
+                using var doc = System.Text.Json.JsonDocument.Parse(json);
+                if (doc.RootElement.TryGetProperty("data", out var data))
+                {
+                    return System.Text.Json.JsonSerializer.Deserialize<PayOrderResponse>(data.GetRawText(), _jsonOptions);
+                }
+                return System.Text.Json.JsonSerializer.Deserialize<PayOrderResponse>(json, _jsonOptions);
+            }
+            catch { return new PayOrderResponse(true, null, null, null, null, null); }
+        }
+        return new PayOrderResponse(false, null, null, null, null, "Payment failed");
+    }
+
+    /// <summary>
+    /// EN: Simple pay order (backward compatible). Returns true if successful.
+    /// VI: Thanh toán order đơn giản (tương thích ngược). Trả về true nếu thành công.
+    /// </summary>
+    public async Task<bool> PayOrderAsync(Guid orderId, Guid shopId, string? paymentMethod = null)
+    {
+        var result = await PayOrderWithDetailsAsync(orderId, shopId, paymentMethod ?? "cash");
+        return result?.Success ?? false;
    }

    // ═══ ACTIVE TABLE ORDERS ═══
--- a/apps/web-client-tpos-net/src/WebClientTpos.Server/Controllers/OrderController.cs
+++ b/apps/web-client-tpos-net/src/WebClientTpos.Server/Controllers/OrderController.cs
@@ -1,6 +1,7 @@
 using System.Text.Json;
 using Microsoft.AspNetCore.Mvc;
 using WebClientTpos.Server.Infrastructure;
+using WebClientTpos.Server.Models;

 namespace WebClientTpos.Server.Controllers;

@@ -114,14 +115,23 @@ public class OrderController : ControllerBase
    }

    /// <summary>
-    /// EN: Pay an order.
-    /// VI: Thanh toán đơn hàng.
+    /// EN: Pay an order — forwards payment method and details to OrderService.
+    /// VI: Thanh toán đơn hàng — chuyển tiếp phương thức thanh toán và chi tiết đến OrderService.
    /// </summary>
    [HttpPost("orders/{orderId:guid}/pay")]
-    public Task<IActionResult> PayOrder(Guid orderId, [FromQuery] Guid? shopId = null)
+    public Task<IActionResult> PayOrder(
+        Guid orderId,
+        [FromQuery] Guid? shopId = null,
+        [FromBody] PayOrderBffRequest? request = null)
    {
        var qs = shopId.HasValue ? $"?shopId={shopId}" : "";
-        return _order.PostAsJsonAsync($"/api/v1/orders/{orderId}/pay{qs}", new { }).ProxyAsync();
+        var body = new
+        {
+            paymentMethod = request?.PaymentMethod ?? "cash",
+            amountTendered = request?.AmountTendered,
+            returnUrl = request?.ReturnUrl
+        };
+        return _order.PostAsJsonAsync($"/api/v1/orders/{orderId}/pay{qs}", body).ProxyAsync();
    }

    /// <summary>
--- a/apps/web-client-tpos-net/src/WebClientTpos.Server/Models/BffDtos.cs
+++ b/apps/web-client-tpos-net/src/WebClientTpos.Server/Models/BffDtos.cs
@@ -47,5 +47,8 @@ public record UpdateTicketStatusRequest(string Status);
 public record CreateRecipeRequest(Guid ShopId, Guid ProductId, string Name, string? Instructions, int PrepTimeMinutes, List<RecipeIngredientRequest>? Ingredients);
 public record RecipeIngredientRequest(string IngredientName, decimal Quantity, string Unit, decimal CostPerUnit);

+// ═══ Payment ═══
+public record PayOrderBffRequest(string? PaymentMethod, decimal? AmountTendered, string? ReturnUrl);
+
 // ═══ Reports (unused DTO kept for reference) ═══
 public record TopProductItem(string ProductName, long TotalSold, decimal TotalRevenue);
--- a/infra/traefik/dynamic/routes.yml
+++ b/infra/traefik/dynamic/routes.yml
@@ -89,6 +89,53 @@ http:
      entryPoints:
        - web

+    # EN: Order Service - Order Management & POS API
+    # VI: Order Service - Quản lý Order & POS API
+    order-service-router:
+      rule: "PathPrefix(`/api/v1/orders`)"
+      service: order-service
+      priority: 100
+      middlewares:
+        - cors
+        - secure-headers
+      entryPoints:
+        - web
+
+    # EN: Order Service - POS/KDS SignalR Hub (WebSocket)
+    # VI: Order Service - POS/KDS SignalR Hub (WebSocket)
+    order-service-hub-router:
+      rule: "PathPrefix(`/hubs/pos`)"
+      service: order-service
+      priority: 110
+      middlewares:
+        - cors
+      entryPoints:
+        - web
+
+    # EN: FnB Engine - Kitchen, Sessions, Tables, Recipes, Reservations
+    # VI: FnB Engine - Bếp, Phiên, Bàn, Công thức, Đặt bàn
+    fnb-engine-router:
+      rule: "PathPrefix(`/api/v1/kitchen`) || PathPrefix(`/api/v1/fnb`)"
+      service: fnb-engine
+      priority: 100
+      middlewares:
+        - cors
+        - secure-headers
+      entryPoints:
+        - web
+
+    # EN: Inventory Service - Stock Management & Deduction
+    # VI: Inventory Service - Quản lý Tồn kho & Trừ kho
+    inventory-service-router:
+      rule: "PathPrefix(`/api/v1/inventory`)"
+      service: inventory-service
+      priority: 100
+      middlewares:
+        - cors
+        - secure-headers
+      entryPoints:
+        - web
+
  services:
    iam-service:
      loadBalancer:
@@ -124,4 +171,25 @@ http:
    merchant-service:
      loadBalancer:
        servers:
-          - url: "http://merchant-service-net:8080"
+          - url: "http://merchant-service-net:8080"
+
+    # EN: Order Service (POS/KDS hub + REST API)
+    # VI: Order Service (POS/KDS hub + REST API)
+    order-service:
+      loadBalancer:
+        servers:
+          - url: "http://order-service-net:8080"
+
+    # EN: FnB Engine
+    # VI: FnB Engine
+    fnb-engine:
+      loadBalancer:
+        servers:
+          - url: "http://fnb-engine-net:8080"
+
+    # EN: Inventory Service
+    # VI: Inventory Service
+    inventory-service:
+      loadBalancer:
+        servers:
+          - url: "http://inventory-service-net:8080"
--- a/services/fnb-engine-net/src/FnbEngine.API/Application/Commands/CreateKitchenTicketCommand.cs
+++ b/services/fnb-engine-net/src/FnbEngine.API/Application/Commands/CreateKitchenTicketCommand.cs
@@ -10,5 +10,7 @@ public record CreateKitchenTicketCommand(
    Guid OrderItemId,
    string ItemName,
    string? Station = null,
-    int Priority = 0
+    int Priority = 0,
+    Guid? ProductId = null,
+    int Quantity = 1
 ) : IRequest<Guid>;
--- a/services/fnb-engine-net/src/FnbEngine.API/Application/Commands/CreateKitchenTicketCommandHandler.cs
+++ b/services/fnb-engine-net/src/FnbEngine.API/Application/Commands/CreateKitchenTicketCommandHandler.cs
@@ -20,7 +20,9 @@ public class CreateKitchenTicketCommandHandler : IRequestHandler<CreateKitchenTi
        var ticket = new KitchenTicket(
            request.SessionId,
            request.OrderItemId,
+            request.ProductId ?? request.OrderItemId,
            request.ItemName,
+            request.Quantity,
            request.Station,
            request.Priority);

--- a/services/fnb-engine-net/src/FnbEngine.API/Application/IntegrationEvents/EventHandlers/KitchenTicketServedDomainEventHandler.cs
+++ b/services/fnb-engine-net/src/FnbEngine.API/Application/IntegrationEvents/EventHandlers/KitchenTicketServedDomainEventHandler.cs
@@ -0,0 +1,141 @@
+// EN: Domain event handler for KitchenTicketServedDomainEvent.
+//     Looks up the recipe for the served product and calls inventory-service to deduct ingredients.
+// VI: Domain event handler cho KitchenTicketServedDomainEvent.
+//     Tra cuu cong thuc cho san pham da phuc vu va goi inventory-service de tru nguyen lieu.
+
+using FnbEngine.Domain.AggregatesModel.RecipeAggregate;
+using FnbEngine.Domain.AggregatesModel.SessionAggregate;
+using FnbEngine.Domain.Events;
+using FnbEngine.Infrastructure.ExternalServices;
+using MediatR;
+using Microsoft.Extensions.Logging;
+
+namespace FnbEngine.API.Application.IntegrationEvents.EventHandlers;
+
+/// <summary>
+/// EN: Handles KitchenTicketServedDomainEvent by looking up recipe and deducting inventory.
+/// VI: Xu ly KitchenTicketServedDomainEvent bang cach tra cuu cong thuc va tru kho.
+/// </summary>
+public class KitchenTicketServedDomainEventHandler : INotificationHandler<KitchenTicketServedDomainEvent>
+{
+    private readonly IRecipeRepository _recipeRepository;
+    private readonly ISessionRepository _sessionRepository;
+    private readonly IInventoryServiceClient _inventoryClient;
+    private readonly ILogger<KitchenTicketServedDomainEventHandler> _logger;
+
+    public KitchenTicketServedDomainEventHandler(
+        IRecipeRepository recipeRepository,
+        ISessionRepository sessionRepository,
+        IInventoryServiceClient inventoryClient,
+        ILogger<KitchenTicketServedDomainEventHandler> logger)
+    {
+        _recipeRepository = recipeRepository ?? throw new ArgumentNullException(nameof(recipeRepository));
+        _sessionRepository = sessionRepository ?? throw new ArgumentNullException(nameof(sessionRepository));
+        _inventoryClient = inventoryClient ?? throw new ArgumentNullException(nameof(inventoryClient));
+        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
+    }
+
+    public async Task Handle(KitchenTicketServedDomainEvent notification, CancellationToken cancellationToken)
+    {
+        var ticket = notification.Ticket;
+
+        _logger.LogInformation(
+            "EN: Kitchen ticket served, starting inventory deduction / VI: Phieu bep da phuc vu, bat dau tru kho - TicketId: {TicketId}, Product: {ProductName}",
+            ticket.Id, ticket.ItemName);
+
+        try
+        {
+            // EN: Get shop ID from the session.
+            // VI: Lay shop ID tu session.
+            var session = await _sessionRepository.GetByIdAsync(ticket.SessionId, cancellationToken);
+            if (session == null)
+            {
+                _logger.LogWarning(
+                    "EN: Session not found for ticket, skipping inventory deduction / VI: Khong tim thay session cho phieu, bo qua tru kho - SessionId: {SessionId}",
+                    ticket.SessionId);
+                return;
+            }
+
+            // EN: Look up the recipe for this product in this shop.
+            // VI: Tra cuu cong thuc cho san pham nay trong shop nay.
+            var recipe = await _recipeRepository.GetByProductIdAndShopAsync(ticket.ProductId, session.ShopId, cancellationToken);
+            if (recipe == null)
+            {
+                _logger.LogInformation(
+                    "EN: No recipe found for product, skipping inventory deduction / VI: Khong tim thay cong thuc cho san pham, bo qua tru kho - ProductId: {ProductId}, ShopId: {ShopId}",
+                    ticket.ProductId, session.ShopId);
+                return;
+            }
+
+            // EN: Filter ingredients that have inventory item links.
+            // VI: Loc nguyen lieu co lien ket den inventory item.
+            var linkedIngredients = recipe.Ingredients
+                .Where(i => i.InventoryItemId.HasValue && i.InventoryItemId.Value != Guid.Empty)
+                .ToList();
+
+            if (linkedIngredients.Count == 0)
+            {
+                _logger.LogInformation(
+                    "EN: Recipe has no linked inventory items, skipping deduction / VI: Cong thuc khong co nguyen lieu lien ket kho, bo qua tru kho - RecipeId: {RecipeId}",
+                    recipe.Id);
+                return;
+            }
+
+            // EN: Build deduction request. Multiply quantity per serving by ticket quantity.
+            // VI: Tao yeu cau tru kho. Nhan so luong moi phan voi so luong phieu.
+            var deductionItems = linkedIngredients.Select(ingredient => new DeductionItemDto(
+                ingredient.InventoryItemId!.Value,
+                ingredient.QuantityPerServing > 0
+                    ? (int)Math.Ceiling(ingredient.QuantityPerServing * ticket.Quantity)
+                    : ticket.Quantity,
+                ingredient.Unit,
+                ingredient.IngredientName
+            )).ToList();
+
+            var request = new DeductInventoryRequest(
+                ShopId: session.ShopId,
+                ReferenceId: ticket.Id,
+                ReferenceType: "KitchenTicket",
+                Reason: $"Auto-deduction for served ticket: {ticket.ItemName} x{ticket.Quantity}",
+                Items: deductionItems);
+
+            // EN: Call inventory service (fire-and-forget style - don't block kitchen flow).
+            // VI: Goi inventory service (kieu fire-and-forget - khong chan luong bep).
+            _ = Task.Run(async () =>
+            {
+                try
+                {
+                    var result = await _inventoryClient.DeductInventoryAsync(request, cancellationToken);
+                    if (result)
+                    {
+                        _logger.LogInformation(
+                            "EN: Inventory deduction successful / VI: Tru kho thanh cong - TicketId: {TicketId}, Items: {ItemCount}",
+                            ticket.Id, deductionItems.Count);
+                    }
+                    else
+                    {
+                        _logger.LogWarning(
+                            "EN: Inventory deduction returned false / VI: Tru kho tra ve false - TicketId: {TicketId}",
+                            ticket.Id);
+                    }
+                }
+                catch (Exception ex)
+                {
+                    // EN: Log but don't throw - inventory deduction should not block kitchen flow.
+                    // VI: Log nhung khong throw - tru kho khong nen chan luong bep.
+                    _logger.LogError(ex,
+                        "EN: Failed to deduct inventory / VI: Tru kho that bai - TicketId: {TicketId}, Error: {Error}",
+                        ticket.Id, ex.Message);
+                }
+            }, cancellationToken);
+        }
+        catch (Exception ex)
+        {
+            // EN: Log but don't throw - inventory deduction should NOT block kitchen workflow.
+            // VI: Log nhung khong throw - tru kho KHONG nen chan luong bep.
+            _logger.LogError(ex,
+                "EN: Error during inventory deduction handling / VI: Loi trong xu ly tru kho - TicketId: {TicketId}",
+                ticket.Id);
+        }
+    }
+}
--- a/services/fnb-engine-net/src/FnbEngine.API/Application/IntegrationEvents/Events/KitchenTicketServedIntegrationEvent.cs
+++ b/services/fnb-engine-net/src/FnbEngine.API/Application/IntegrationEvents/Events/KitchenTicketServedIntegrationEvent.cs
@@ -0,0 +1,19 @@
+// EN: Integration event published when a kitchen ticket is served.
+// VI: Integration event phat ra khi phieu bep duoc phuc vu.
+
+using MediatR;
+
+namespace FnbEngine.API.Application.IntegrationEvents.Events;
+
+/// <summary>
+/// EN: Integration event for cross-service communication when a kitchen ticket is served.
+/// VI: Integration event cho giao tiep giua cac services khi phieu bep duoc phuc vu.
+/// </summary>
+public record KitchenTicketServedIntegrationEvent(
+    Guid TicketId,
+    Guid OrderItemId,
+    Guid ProductId,
+    Guid ShopId,
+    string ProductName,
+    int Quantity,
+    DateTime ServedAt) : INotification;
--- a/services/fnb-engine-net/src/FnbEngine.API/Controllers/KitchenController.cs
+++ b/services/fnb-engine-net/src/FnbEngine.API/Controllers/KitchenController.cs
@@ -86,14 +86,16 @@ public class KitchenController : ControllerBase
            await _sessionRepository.UnitOfWork.SaveEntitiesAsync(ct);
        }

-        // EN: Create kitchen ticket via MediatR
-        // VI: Tạo phiếu bếp qua MediatR
+        // EN: Create kitchen ticket via MediatR (with ProductId and Quantity for inventory deduction)
+        // VI: Tạo phiếu bếp qua MediatR (với ProductId và Quantity cho trừ kho)
        var ticketId = await _mediator.Send(new CreateKitchenTicketCommand(
            activeSession.Id,
            request.ProductId,
            request.ProductName,
            null,
-            0
+            0,
+            request.ProductId,
+            request.Quantity
        ), ct);

        return Ok(new CreateTicketResponse(ticketId));
--- a/services/fnb-engine-net/src/FnbEngine.Domain/AggregatesModel/KitchenAggregate/KitchenTicket.cs
+++ b/services/fnb-engine-net/src/FnbEngine.Domain/AggregatesModel/KitchenAggregate/KitchenTicket.cs
@@ -1,6 +1,7 @@
 // EN: Kitchen ticket entity for kitchen display.
 // VI: Entity KitchenTicket cho hiển thị bếp.

+using FnbEngine.Domain.Events;
 using FnbEngine.Domain.SeedWork;

 namespace FnbEngine.Domain.AggregatesModel.KitchenAggregate;
@@ -13,18 +14,32 @@ public class KitchenTicket : Entity, IAggregateRoot
 {
    private Guid _sessionId;
    private Guid _orderItemId;
+    private Guid _productId;
    private string _itemName = null!;
    private string? _station; // Bar, Kitchen, Grill, etc.
    private int _priority;
+    private int _quantity;
    private string _status = null!; // Pending, InProgress, Ready, Served
    private DateTime _createdAt;
    private DateTime? _completedAt;

    public Guid SessionId => _sessionId;
    public Guid OrderItemId => _orderItemId;
+
+    /// <summary>
+    /// EN: Product ID from Catalog Service (for recipe lookup).
+    /// VI: ID san pham tu Catalog Service (de tra cuu cong thuc).
+    /// </summary>
+    public Guid ProductId => _productId;
    public string ItemName => _itemName;
    public string? Station => _station;
    public int Priority => _priority;
+
+    /// <summary>
+    /// EN: Quantity of items ordered.
+    /// VI: So luong item da dat.
+    /// </summary>
+    public int Quantity => _quantity;
    public string Status => _status;
    public DateTime CreatedAt => _createdAt;
    public DateTime? CompletedAt => _completedAt;
@@ -34,11 +49,22 @@ public class KitchenTicket : Entity, IAggregateRoot
    }

    public KitchenTicket(Guid sessionId, Guid orderItemId, string itemName, string? station = null, int priority = 0)
+        : this(sessionId, orderItemId, orderItemId, itemName, 1, station, priority)
+    {
+    }
+
+    /// <summary>
+    /// EN: Create a kitchen ticket with product ID and quantity.
+    /// VI: Tao phieu bep voi product ID va so luong.
+    /// </summary>
+    public KitchenTicket(Guid sessionId, Guid orderItemId, Guid productId, string itemName, int quantity = 1, string? station = null, int priority = 0)
    {
        Id = Guid.NewGuid();
        _sessionId = sessionId;
        _orderItemId = orderItemId;
+        _productId = productId;
        _itemName = itemName;
+        _quantity = quantity > 0 ? quantity : 1;
        _station = station;
        _priority = priority;
        _status = "Pending";
@@ -56,8 +82,16 @@ public class KitchenTicket : Entity, IAggregateRoot
        _completedAt = DateTime.UtcNow;
    }

+    /// <summary>
+    /// EN: Mark ticket as served and raise domain event for inventory deduction.
+    /// VI: Danh dau phieu da phuc vu va phat domain event de tru kho.
+    /// </summary>
    public void MarkAsServed()
    {
        _status = "Served";
+
+        // EN: Raise domain event for inventory auto-deduction.
+        // VI: Phat domain event de tu dong tru kho.
+        AddDomainEvent(new KitchenTicketServedDomainEvent(this));
    }
 }
--- a/services/fnb-engine-net/src/FnbEngine.Domain/Events/KitchenTicketServedDomainEvent.cs
+++ b/services/fnb-engine-net/src/FnbEngine.Domain/Events/KitchenTicketServedDomainEvent.cs
@@ -0,0 +1,13 @@
+// EN: Domain event raised when a kitchen ticket is marked as served.
+// VI: Domain event phat ra khi phieu bep duoc danh dau da phuc vu.
+
+using FnbEngine.Domain.AggregatesModel.KitchenAggregate;
+using MediatR;
+
+namespace FnbEngine.Domain.Events;
+
+/// <summary>
+/// EN: Domain event raised when a kitchen ticket status changes to Served.
+/// VI: Domain event phat ra khi trang thai phieu bep chuyen sang Served.
+/// </summary>
+public record KitchenTicketServedDomainEvent(KitchenTicket Ticket) : INotification;
--- a/services/fnb-engine-net/src/FnbEngine.Infrastructure/DependencyInjection.cs
+++ b/services/fnb-engine-net/src/FnbEngine.Infrastructure/DependencyInjection.cs
@@ -6,8 +6,11 @@ using FnbEngine.Domain.AggregatesModel.SessionAggregate;
 using FnbEngine.Domain.AggregatesModel.KitchenAggregate;
 using FnbEngine.Domain.AggregatesModel.RecipeAggregate;
 using FnbEngine.Domain.AggregatesModel.ReservationAggregate;
+using FnbEngine.Infrastructure.ExternalServices;
 using FnbEngine.Infrastructure.Idempotency;
 using FnbEngine.Infrastructure.Repositories;
+using Polly;
+using Polly.Extensions.Http;

 namespace FnbEngine.Infrastructure;

@@ -60,6 +63,30 @@ public static class DependencyInjection
        // EN: Register idempotency services / VI: Đăng ký idempotency services
        services.AddScoped<IRequestManager, RequestManager>();

+        // EN: Register inventory service HTTP client with Polly retry policy.
+        // VI: Đăng ký HTTP client inventory service với Polly retry policy.
+        var inventoryServiceUrl = configuration["Services:InventoryService:BaseUrl"]
+            ?? configuration["INVENTORY_SERVICE_URL"]
+            ?? "http://inventory-service:8080";
+
+        services.AddHttpClient<IInventoryServiceClient, InventoryServiceClient>(client =>
+        {
+            client.BaseAddress = new Uri(inventoryServiceUrl);
+            client.Timeout = TimeSpan.FromSeconds(10);
+        })
+        .AddPolicyHandler(HttpPolicyExtensions
+            .HandleTransientHttpError()
+            .WaitAndRetryAsync(3, retryAttempt =>
+                TimeSpan.FromSeconds(Math.Pow(2, retryAttempt)),
+                onRetry: (outcome, timespan, retryAttempt, context) =>
+                {
+                    // EN: Log retry attempts / VI: Log các lần thử lại
+                    Console.WriteLine($"Retry {retryAttempt} for inventory deduction after {timespan.TotalSeconds}s");
+                }))
+        .AddPolicyHandler(HttpPolicyExtensions
+            .HandleTransientHttpError()
+            .CircuitBreakerAsync(5, TimeSpan.FromSeconds(30)));
+
        return services;
    }
 }
--- a/services/fnb-engine-net/src/FnbEngine.Infrastructure/EntityConfigurations/KitchenTicketEntityTypeConfiguration.cs
+++ b/services/fnb-engine-net/src/FnbEngine.Infrastructure/EntityConfigurations/KitchenTicketEntityTypeConfiguration.cs
@@ -31,6 +31,10 @@ public class KitchenTicketEntityTypeConfiguration : IEntityTypeConfiguration<Kit
            .HasColumnName("order_item_id")
            .IsRequired();

+        builder.Property(kt => kt.ProductId)
+            .HasColumnName("product_id")
+            .IsRequired();
+
        builder.Property(kt => kt.ItemName)
            .HasColumnName("item_name")
            .HasMaxLength(200)
@@ -44,6 +48,11 @@ public class KitchenTicketEntityTypeConfiguration : IEntityTypeConfiguration<Kit
            .HasColumnName("priority")
            .IsRequired();

+        builder.Property(kt => kt.Quantity)
+            .HasColumnName("quantity")
+            .IsRequired()
+            .HasDefaultValue(1);
+
        builder.Property(kt => kt.Status)
            .HasColumnName("status")
            .HasMaxLength(50)
@@ -56,6 +65,8 @@ public class KitchenTicketEntityTypeConfiguration : IEntityTypeConfiguration<Kit
        builder.Property(kt => kt.CompletedAt)
            .HasColumnName("completed_at");

+        builder.Ignore(kt => kt.DomainEvents);
+
        // EN: Index for querying by session
        // VI: Index để query theo phiên
        builder.HasIndex(kt => kt.SessionId)
--- a/services/fnb-engine-net/src/FnbEngine.Infrastructure/ExternalServices/IInventoryServiceClient.cs
+++ b/services/fnb-engine-net/src/FnbEngine.Infrastructure/ExternalServices/IInventoryServiceClient.cs
@@ -0,0 +1,38 @@
+// EN: Interface for inventory service HTTP client.
+// VI: Interface cho HTTP client cua inventory service.
+
+namespace FnbEngine.Infrastructure.ExternalServices;
+
+/// <summary>
+/// EN: Client interface for calling inventory-service API.
+/// VI: Interface client de goi API cua inventory-service.
+/// </summary>
+public interface IInventoryServiceClient
+{
+    /// <summary>
+    /// EN: Deduct inventory items (bulk deduction via inventory-service API).
+    /// VI: Tru kho (tru hang loat qua API inventory-service).
+    /// </summary>
+    Task<bool> DeductInventoryAsync(DeductInventoryRequest request, CancellationToken cancellationToken = default);
+}
+
+/// <summary>
+/// EN: Request DTO for bulk inventory deduction.
+/// VI: DTO request cho tru kho hang loat.
+/// </summary>
+public record DeductInventoryRequest(
+    Guid ShopId,
+    Guid ReferenceId,
+    string ReferenceType,
+    string Reason,
+    List<DeductionItemDto> Items);
+
+/// <summary>
+/// EN: Individual item to deduct from inventory.
+/// VI: Item rieng le de tru tu kho.
+/// </summary>
+public record DeductionItemDto(
+    Guid InventoryItemId,
+    int Amount,
+    string Unit,
+    string IngredientName);
--- a/services/fnb-engine-net/src/FnbEngine.Infrastructure/ExternalServices/InventoryServiceClient.cs
+++ b/services/fnb-engine-net/src/FnbEngine.Infrastructure/ExternalServices/InventoryServiceClient.cs
@@ -0,0 +1,81 @@
+// EN: HTTP client implementation for calling inventory-service API.
+// VI: Trien khai HTTP client de goi API cua inventory-service.
+
+using System.Net.Http.Json;
+using System.Text.Json;
+using Microsoft.Extensions.Logging;
+
+namespace FnbEngine.Infrastructure.ExternalServices;
+
+/// <summary>
+/// EN: HTTP client for inventory-service with Polly retry policies.
+/// VI: HTTP client cho inventory-service voi Polly retry policies.
+/// </summary>
+public class InventoryServiceClient : IInventoryServiceClient
+{
+    private readonly HttpClient _httpClient;
+    private readonly ILogger<InventoryServiceClient> _logger;
+
+    private static readonly JsonSerializerOptions JsonOptions = new()
+    {
+        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
+        PropertyNameCaseInsensitive = true
+    };
+
+    public InventoryServiceClient(
+        HttpClient httpClient,
+        ILogger<InventoryServiceClient> logger)
+    {
+        _httpClient = httpClient ?? throw new ArgumentNullException(nameof(httpClient));
+        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
+    }
+
+    /// <summary>
+    /// EN: Deduct inventory by calling POST /api/v1/inventory/deduct on inventory-service.
+    /// VI: Tru kho bang cach goi POST /api/v1/inventory/deduct tren inventory-service.
+    /// </summary>
+    public async Task<bool> DeductInventoryAsync(DeductInventoryRequest request, CancellationToken cancellationToken = default)
+    {
+        _logger.LogInformation(
+            "EN: Sending inventory deduction request / VI: Gui yeu cau tru kho - ReferenceId: {ReferenceId}, Items: {ItemCount}",
+            request.ReferenceId, request.Items.Count);
+
+        try
+        {
+            var response = await _httpClient.PostAsJsonAsync(
+                "api/v1/inventory/deduct",
+                request,
+                JsonOptions,
+                cancellationToken);
+
+            if (response.IsSuccessStatusCode)
+            {
+                _logger.LogInformation(
+                    "EN: Inventory deduction API call succeeded / VI: Goi API tru kho thanh cong - ReferenceId: {ReferenceId}",
+                    request.ReferenceId);
+                return true;
+            }
+
+            var errorContent = await response.Content.ReadAsStringAsync(cancellationToken);
+            _logger.LogWarning(
+                "EN: Inventory deduction API call failed / VI: Goi API tru kho that bai - StatusCode: {StatusCode}, Error: {Error}",
+                response.StatusCode, errorContent);
+
+            return false;
+        }
+        catch (HttpRequestException ex)
+        {
+            _logger.LogError(ex,
+                "EN: HTTP error calling inventory service / VI: Loi HTTP khi goi inventory service - ReferenceId: {ReferenceId}",
+                request.ReferenceId);
+            return false;
+        }
+        catch (TaskCanceledException ex)
+        {
+            _logger.LogWarning(ex,
+                "EN: Inventory service call timed out / VI: Goi inventory service bi timeout - ReferenceId: {ReferenceId}",
+                request.ReferenceId);
+            return false;
+        }
+    }
+}
--- a/services/inventory-service-net/src/InventoryService.API/Application/Commands/DeductInventory/DeductInventoryCommand.cs
+++ b/services/inventory-service-net/src/InventoryService.API/Application/Commands/DeductInventory/DeductInventoryCommand.cs
@@ -0,0 +1,47 @@
+// EN: Command for bulk inventory deduction (triggered by kitchen ticket served).
+// VI: Command trừ kho hàng loạt (được kích hoạt khi phiếu bếp đã phục vụ).
+
+using MediatR;
+
+namespace InventoryService.API.Application.Commands.DeductInventory;
+
+/// <summary>
+/// EN: Command to deduct multiple inventory items in a single operation.
+/// VI: Command để trừ nhiều inventory items trong một thao tác.
+/// </summary>
+public record DeductInventoryCommand(
+    Guid ShopId,
+    Guid ReferenceId,
+    string ReferenceType,
+    string Reason,
+    List<DeductionItem> Items) : IRequest<DeductInventoryResult>;
+
+/// <summary>
+/// EN: Individual item to deduct from inventory.
+/// VI: Item riêng lẻ để trừ từ kho.
+/// </summary>
+public record DeductionItem(
+    Guid InventoryItemId,
+    int Amount,
+    string Unit,
+    string IngredientName);
+
+/// <summary>
+/// EN: Result of bulk inventory deduction.
+/// VI: Kết quả trừ kho hàng loạt.
+/// </summary>
+public record DeductInventoryResult(
+    bool Success,
+    int ItemsDeducted,
+    int ItemsSkipped,
+    List<DeductionResultItem> Items);
+
+/// <summary>
+/// EN: Result for each individual deduction item.
+/// VI: Kết quả cho mỗi item trừ kho riêng lẻ.
+/// </summary>
+public record DeductionResultItem(
+    Guid InventoryItemId,
+    string IngredientName,
+    bool Deducted,
+    string? Error);
--- a/services/inventory-service-net/src/InventoryService.API/Application/Commands/DeductInventory/DeductInventoryCommandHandler.cs
+++ b/services/inventory-service-net/src/InventoryService.API/Application/Commands/DeductInventory/DeductInventoryCommandHandler.cs
@@ -0,0 +1,146 @@
+// EN: Handler for DeductInventoryCommand - performs bulk deduction with idempotency.
+// VI: Handler cho DeductInventoryCommand - thực hiện trừ kho hàng loạt với idempotency.
+
+using InventoryService.Domain.AggregatesModel.InventoryAggregate;
+using InventoryService.Infrastructure.Idempotency;
+using MediatR;
+using Microsoft.Extensions.Logging;
+
+namespace InventoryService.API.Application.Commands.DeductInventory;
+
+/// <summary>
+/// EN: Handles bulk inventory deduction for kitchen ticket served events.
+/// VI: Xử lý trừ kho hàng loạt cho sự kiện phiếu bếp đã phục vụ.
+/// </summary>
+public class DeductInventoryCommandHandler : IRequestHandler<DeductInventoryCommand, DeductInventoryResult>
+{
+    private readonly IInventoryRepository _repository;
+    private readonly IRequestManager _requestManager;
+    private readonly ILogger<DeductInventoryCommandHandler> _logger;
+
+    public DeductInventoryCommandHandler(
+        IInventoryRepository repository,
+        IRequestManager requestManager,
+        ILogger<DeductInventoryCommandHandler> logger)
+    {
+        _repository = repository ?? throw new ArgumentNullException(nameof(repository));
+        _requestManager = requestManager ?? throw new ArgumentNullException(nameof(requestManager));
+        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
+    }
+
+    public async Task<DeductInventoryResult> Handle(DeductInventoryCommand request, CancellationToken cancellationToken)
+    {
+        // EN: Idempotency check - don't deduct twice for the same reference.
+        // VI: Kiểm tra idempotency - không trừ hai lần cho cùng một reference.
+        if (await _requestManager.ExistAsync(request.ReferenceId))
+        {
+            _logger.LogWarning(
+                "EN: Duplicate deduction request detected, skipping / VI: Phát hiện yêu cầu trừ kho trùng lặp, bỏ qua - ReferenceId: {ReferenceId}",
+                request.ReferenceId);
+
+            return new DeductInventoryResult(
+                Success: true,
+                ItemsDeducted: 0,
+                ItemsSkipped: request.Items.Count,
+                Items: request.Items.Select(i => new DeductionResultItem(
+                    i.InventoryItemId, i.IngredientName, false, "Duplicate request")).ToList());
+        }
+
+        // EN: Record this request for idempotency.
+        // VI: Ghi nhận request này cho idempotency.
+        await _requestManager.CreateRequestForCommandAsync<DeductInventoryCommand>(request.ReferenceId);
+
+        var resultItems = new List<DeductionResultItem>();
+        var itemsDeducted = 0;
+        var itemsSkipped = 0;
+
+        foreach (var deductionItem in request.Items)
+        {
+            try
+            {
+                var inventoryItem = await _repository.GetByIdAsync(deductionItem.InventoryItemId, cancellationToken);
+
+                if (inventoryItem == null)
+                {
+                    _logger.LogWarning(
+                        "EN: Inventory item not found for deduction / VI: Không tìm thấy inventory item để trừ - ItemId: {ItemId}, Ingredient: {Ingredient}",
+                        deductionItem.InventoryItemId, deductionItem.IngredientName);
+
+                    resultItems.Add(new DeductionResultItem(
+                        deductionItem.InventoryItemId, deductionItem.IngredientName, false, "Item not found"));
+                    itemsSkipped++;
+                    continue;
+                }
+
+                // EN: Check if sufficient stock is available.
+                // VI: Kiểm tra xem có đủ stock hay không.
+                if (inventoryItem.AvailableQuantity < deductionItem.Amount)
+                {
+                    _logger.LogWarning(
+                        "EN: Insufficient stock for deduction / VI: Không đủ stock để trừ - ItemId: {ItemId}, Available: {Available}, Requested: {Requested}",
+                        deductionItem.InventoryItemId, inventoryItem.AvailableQuantity, deductionItem.Amount);
+
+                    // EN: Deduct what's available instead of failing entirely.
+                    // VI: Trừ những gì có sẵn thay vì thất bại hoàn toàn.
+                    if (inventoryItem.AvailableQuantity > 0)
+                    {
+                        inventoryItem.StockOut(
+                            inventoryItem.AvailableQuantity,
+                            $"[Partial] {request.Reason} (requested: {deductionItem.Amount}, available: {inventoryItem.AvailableQuantity})",
+                            request.ReferenceId);
+
+                        resultItems.Add(new DeductionResultItem(
+                            deductionItem.InventoryItemId, deductionItem.IngredientName, true,
+                            $"Partial deduction: {inventoryItem.AvailableQuantity} of {deductionItem.Amount}"));
+                        itemsDeducted++;
+                    }
+                    else
+                    {
+                        resultItems.Add(new DeductionResultItem(
+                            deductionItem.InventoryItemId, deductionItem.IngredientName, false, "Insufficient stock (0 available)"));
+                        itemsSkipped++;
+                    }
+                    continue;
+                }
+
+                // EN: Perform the deduction.
+                // VI: Thực hiện trừ kho.
+                inventoryItem.StockOut(deductionItem.Amount, request.Reason, request.ReferenceId);
+
+                resultItems.Add(new DeductionResultItem(
+                    deductionItem.InventoryItemId, deductionItem.IngredientName, true, null));
+                itemsDeducted++;
+
+                _logger.LogInformation(
+                    "EN: Deducted inventory / VI: Đã trừ kho - ItemId: {ItemId}, Amount: {Amount}, Ingredient: {Ingredient}",
+                    deductionItem.InventoryItemId, deductionItem.Amount, deductionItem.IngredientName);
+            }
+            catch (Exception ex)
+            {
+                // EN: Log error for individual item but continue with remaining items.
+                // VI: Log lỗi cho item riêng lẻ nhưng tiếp tục với các items còn lại.
+                _logger.LogError(ex,
+                    "EN: Error deducting inventory item / VI: Lỗi trừ inventory item - ItemId: {ItemId}",
+                    deductionItem.InventoryItemId);
+
+                resultItems.Add(new DeductionResultItem(
+                    deductionItem.InventoryItemId, deductionItem.IngredientName, false, ex.Message));
+                itemsSkipped++;
+            }
+        }
+
+        // EN: Save all changes in one transaction.
+        // VI: Lưu tất cả thay đổi trong một transaction.
+        await _repository.UnitOfWork.SaveEntitiesAsync(cancellationToken);
+
+        _logger.LogInformation(
+            "EN: Bulk inventory deduction completed / VI: Trừ kho hàng loạt hoàn thành - ReferenceId: {ReferenceId}, Deducted: {Deducted}, Skipped: {Skipped}",
+            request.ReferenceId, itemsDeducted, itemsSkipped);
+
+        return new DeductInventoryResult(
+            Success: itemsDeducted > 0,
+            ItemsDeducted: itemsDeducted,
+            ItemsSkipped: itemsSkipped,
+            Items: resultItems);
+    }
+}
--- a/services/inventory-service-net/src/InventoryService.API/Application/DTOs/InventoryDtos.cs
+++ b/services/inventory-service-net/src/InventoryService.API/Application/DTOs/InventoryDtos.cs
@@ -124,6 +124,27 @@ public record StocktakeRequest(Guid ShopId, List<StocktakeItemRequest> Items);

 public record StocktakeItemRequest(Guid InventoryItemId, int CountedQuantity);

+/// <summary>
+/// EN: Request for bulk inventory deduction (from kitchen ticket served).
+/// VI: Request cho trừ kho hàng loạt (từ phiếu bếp đã phục vụ).
+/// </summary>
+public record DeductInventoryRequest(
+    Guid ShopId,
+    Guid ReferenceId,
+    string ReferenceType,
+    string? Reason,
+    List<DeductionItemRequest> Items);
+
+/// <summary>
+/// EN: Individual deduction item in a bulk deduction request.
+/// VI: Item trừ kho riêng lẻ trong yêu cầu trừ kho hàng loạt.
+/// </summary>
+public record DeductionItemRequest(
+    Guid InventoryItemId,
+    int Amount,
+    string Unit,
+    string IngredientName);
+
 public class ApiResponse<T>
 {
    public bool Success { get; set; }
--- a/services/inventory-service-net/src/InventoryService.API/Application/Validations/DeductInventoryCommandValidator.cs
+++ b/services/inventory-service-net/src/InventoryService.API/Application/Validations/DeductInventoryCommandValidator.cs
@@ -0,0 +1,44 @@
+// EN: FluentValidation validator for DeductInventoryCommand.
+// VI: FluentValidation validator cho DeductInventoryCommand.
+
+using FluentValidation;
+using InventoryService.API.Application.Commands.DeductInventory;
+
+namespace InventoryService.API.Application.Validations;
+
+/// <summary>
+/// EN: Validates DeductInventoryCommand before processing.
+/// VI: Validate DeductInventoryCommand trước khi xử lý.
+/// </summary>
+public class DeductInventoryCommandValidator : AbstractValidator<DeductInventoryCommand>
+{
+    public DeductInventoryCommandValidator()
+    {
+        RuleFor(x => x.ShopId)
+            .NotEmpty()
+            .WithMessage("Shop ID is required / Shop ID là bắt buộc");
+
+        RuleFor(x => x.ReferenceId)
+            .NotEmpty()
+            .WithMessage("Reference ID is required / Reference ID là bắt buộc");
+
+        RuleFor(x => x.ReferenceType)
+            .NotEmpty()
+            .WithMessage("Reference type is required / Loại tham chiếu là bắt buộc");
+
+        RuleFor(x => x.Items)
+            .NotEmpty()
+            .WithMessage("At least one deduction item is required / Cần ít nhất một item trừ kho");
+
+        RuleForEach(x => x.Items).ChildRules(item =>
+        {
+            item.RuleFor(i => i.InventoryItemId)
+                .NotEmpty()
+                .WithMessage("Inventory item ID is required / Inventory item ID là bắt buộc");
+
+            item.RuleFor(i => i.Amount)
+                .GreaterThan(0)
+                .WithMessage("Amount must be positive / Số lượng phải dương");
+        });
+    }
+}
--- a/services/inventory-service-net/src/InventoryService.API/Controllers/InventoryController.cs
+++ b/services/inventory-service-net/src/InventoryService.API/Controllers/InventoryController.cs
@@ -2,6 +2,7 @@
 // VI: Controller chính cho các thao tác Inventory.

 using InventoryService.API.Application.Commands;
+using InventoryService.API.Application.Commands.DeductInventory;
 using InventoryService.API.Application.DTOs;
 using InventoryService.API.Application.Queries;
 using MediatR;
@@ -440,6 +441,39 @@ public class InventoryController : ControllerBase
        return Ok(ApiResponse<PagedResult<InventoryTransactionDto>>.Ok(result));
    }

+    /// <summary>
+    /// EN: Bulk deduct inventory items (called by fnb-engine when kitchen ticket is served).
+    /// VI: Trừ kho hàng loạt (được gọi bởi fnb-engine khi phiếu bếp đã phục vụ).
+    /// </summary>
+    [HttpPost("deduct")]
+    [SwaggerOperation(Summary = "Bulk deduct inventory items (cross-service: kitchen ticket served)")]
+    [SwaggerResponse(200, "Deduction processed")]
+    [SwaggerResponse(400, "Invalid request")]
+    public async Task<ActionResult<ApiResponse<DeductInventoryResult>>> DeductInventory(
+        [FromBody] DeductInventoryRequest request,
+        CancellationToken ct = default)
+    {
+        try
+        {
+            var command = new DeductInventoryCommand(
+                request.ShopId,
+                request.ReferenceId,
+                request.ReferenceType,
+                request.Reason ?? "Kitchen ticket deduction",
+                request.Items.Select(i => new DeductionItem(
+                    i.InventoryItemId, i.Amount, i.Unit, i.IngredientName)).ToList());
+
+            var result = await _mediator.Send(command, ct);
+
+            return Ok(ApiResponse<DeductInventoryResult>.Ok(result));
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "EN: Error processing inventory deduction / VI: Lỗi xử lý trừ kho");
+            return BadRequest(ApiResponse<DeductInventoryResult>.Fail(ex.Message));
+        }
+    }
+
    /// <summary>
    /// EN: Get low stock items.
    /// VI: Lấy các items stock thấp.
--- a/services/inventory-service-net/src/InventoryService.Infrastructure/InventoryContext.cs
+++ b/services/inventory-service-net/src/InventoryService.Infrastructure/InventoryContext.cs
@@ -4,6 +4,7 @@ using Microsoft.EntityFrameworkCore.Storage;
 using InventoryService.Domain.AggregatesModel.InventoryAggregate;
 using InventoryService.Domain.SeedWork;
 using InventoryService.Infrastructure.EntityConfigurations;
+using InventoryService.Infrastructure.Idempotency;

 namespace InventoryService.Infrastructure;

@@ -21,6 +22,7 @@ public class InventoryContext : DbContext, IUnitOfWork
    /// VI: Bảng Inventory items.
    /// </summary>
    public DbSet<InventoryItem> InventoryItems => Set<InventoryItem>();
+    public DbSet<ClientRequest> ClientRequests => Set<ClientRequest>();

    /// <summary>
    /// EN: Read-only access to current transaction.
@@ -44,6 +46,17 @@ public class InventoryContext : DbContext, IUnitOfWork
    {
        modelBuilder.ApplyConfiguration(new InventoryItemEntityTypeConfiguration());

+        // EN: Configure ClientRequest for idempotency tracking.
+        // VI: Cấu hình ClientRequest cho theo dõi idempotency.
+        modelBuilder.Entity<ClientRequest>(b =>
+        {
+            b.ToTable("client_requests");
+            b.HasKey(cr => cr.Id);
+            b.Property(cr => cr.Id).HasColumnName("id");
+            b.Property(cr => cr.Name).HasColumnName("name").HasMaxLength(200).IsRequired();
+            b.Property(cr => cr.Time).HasColumnName("time").IsRequired();
+        });
+
        // EN: Ignore Enumeration types so EF Core does NOT auto-discover TypeId as a FK.
        //     TransactionType and ItemType are DDD Enumerations resolved in-memory.
        // VI: Ignore các Enumeration type để EF Core KHÔNG tự phát hiện TypeId là FK.
--- a/services/order-service-net/src/OrderService.API/Application/Commands/CancelOrderCommandHandler.cs
+++ b/services/order-service-net/src/OrderService.API/Application/Commands/CancelOrderCommandHandler.cs
@@ -2,6 +2,7 @@
 // VI: Handler cho CancelOrderCommand.

 using MediatR;
+using OrderService.API.Hubs;
 using OrderService.Domain.AggregatesModel.OrderAggregate;
 using OrderService.Domain.Exceptions;

@@ -14,13 +15,16 @@ namespace OrderService.API.Application.Commands;
 public class CancelOrderCommandHandler : IRequestHandler<CancelOrderCommand, CancelOrderResult>
 {
    private readonly IOrderRepository _orderRepository;
+    private readonly IPosNotificationService _posNotificationService;
    private readonly ILogger<CancelOrderCommandHandler> _logger;

    public CancelOrderCommandHandler(
        IOrderRepository orderRepository,
+        IPosNotificationService posNotificationService,
        ILogger<CancelOrderCommandHandler> logger)
    {
        _orderRepository = orderRepository ?? throw new ArgumentNullException(nameof(orderRepository));
+        _posNotificationService = posNotificationService ?? throw new ArgumentNullException(nameof(posNotificationService));
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
    }

@@ -60,6 +64,20 @@ public class CancelOrderCommandHandler : IRequestHandler<CancelOrderCommand, Can
            order.Id,
            request.Reason);

+        // EN: Send real-time cancellation notification / VI: Gửi thông báo hủy order real-time
+        try
+        {
+            await _posNotificationService.NotifyOrderStatusChangedAsync(
+                order.ShopId, order.Id, "Active", order.Status.Name, cancellationToken);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogWarning(ex,
+                "EN: Failed to send POS notification for order {OrderId} / " +
+                "VI: Gửi thông báo POS thất bại cho order {OrderId}",
+                order.Id);
+        }
+
        return new CancelOrderResult(true, order.Status.Name);
    }
 }
--- a/services/order-service-net/src/OrderService.API/Application/Commands/CompleteOrderCommandHandler.cs
+++ b/services/order-service-net/src/OrderService.API/Application/Commands/CompleteOrderCommandHandler.cs
@@ -2,6 +2,7 @@
 // VI: Handler cho CompleteOrderCommand.

 using MediatR;
+using OrderService.API.Hubs;
 using OrderService.Domain.AggregatesModel.OrderAggregate;
 using OrderService.Domain.Exceptions;

@@ -14,13 +15,16 @@ namespace OrderService.API.Application.Commands;
 public class CompleteOrderCommandHandler : IRequestHandler<CompleteOrderCommand, CompleteOrderResult>
 {
    private readonly IOrderRepository _orderRepository;
+    private readonly IPosNotificationService _posNotificationService;
    private readonly ILogger<CompleteOrderCommandHandler> _logger;

    public CompleteOrderCommandHandler(
        IOrderRepository orderRepository,
+        IPosNotificationService posNotificationService,
        ILogger<CompleteOrderCommandHandler> logger)
    {
        _orderRepository = orderRepository ?? throw new ArgumentNullException(nameof(orderRepository));
+        _posNotificationService = posNotificationService ?? throw new ArgumentNullException(nameof(posNotificationService));
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
    }

@@ -59,6 +63,20 @@ public class CompleteOrderCommandHandler : IRequestHandler<CompleteOrderCommand,
            "EN: Order completed successfully / VI: Hoàn thành order thành công: {OrderId}",
            order.Id);

+        // EN: Send real-time status change notification / VI: Gửi thông báo thay đổi trạng thái real-time
+        try
+        {
+            await _posNotificationService.NotifyOrderStatusChangedAsync(
+                order.ShopId, order.Id, "Processing", order.Status.Name, cancellationToken);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogWarning(ex,
+                "EN: Failed to send POS notification for order {OrderId} / " +
+                "VI: Gửi thông báo POS thất bại cho order {OrderId}",
+                order.Id);
+        }
+
        return new CompleteOrderResult(true, order.Status.Name);
    }
 }
--- a/services/order-service-net/src/OrderService.API/Application/Commands/CompleteOrderPaymentCommand.cs
+++ b/services/order-service-net/src/OrderService.API/Application/Commands/CompleteOrderPaymentCommand.cs
@@ -0,0 +1,27 @@
+// EN: Command to complete order payment after gateway callback confirmation.
+// VI: Command hoàn tất thanh toán order sau khi nhận callback xác nhận từ cổng thanh toán.
+
+using MediatR;
+
+namespace OrderService.API.Application.Commands;
+
+/// <summary>
+/// EN: Command triggered by payment gateway callback to finalize order payment.
+/// VI: Command được kích hoạt bởi callback cổng thanh toán để hoàn tất thanh toán order.
+/// </summary>
+public record CompleteOrderPaymentCommand(
+    Guid OrderId,
+    string GatewayTransactionId,   // EN: Transaction ID from payment gateway / VI: Mã giao dịch từ cổng thanh toán
+    bool IsSuccess,                 // EN: Whether payment was successful / VI: Thanh toán có thành công không
+    string? GatewayResponseCode     // EN: Response code from gateway / VI: Mã phản hồi từ cổng thanh toán
+) : IRequest<CompleteOrderPaymentResult>;
+
+/// <summary>
+/// EN: Result of completing order payment.
+/// VI: Kết quả hoàn tất thanh toán order.
+/// </summary>
+public record CompleteOrderPaymentResult(
+    bool Success,
+    string Status,
+    string? ErrorMessage
+);
--- a/services/order-service-net/src/OrderService.API/Application/Commands/CompleteOrderPaymentCommandHandler.cs
+++ b/services/order-service-net/src/OrderService.API/Application/Commands/CompleteOrderPaymentCommandHandler.cs
@@ -0,0 +1,82 @@
+// EN: Handler for CompleteOrderPaymentCommand — finalizes payment after gateway callback.
+// VI: Handler cho CompleteOrderPaymentCommand — hoàn tất thanh toán sau callback cổng thanh toán.
+
+using MediatR;
+using OrderService.Domain.AggregatesModel.OrderAggregate;
+using OrderService.Domain.Exceptions;
+
+namespace OrderService.API.Application.Commands;
+
+/// <summary>
+/// EN: Handler for completing order payment after online gateway confirmation.
+/// VI: Handler hoàn tất thanh toán order sau xác nhận cổng thanh toán trực tuyến.
+/// </summary>
+public class CompleteOrderPaymentCommandHandler : IRequestHandler<CompleteOrderPaymentCommand, CompleteOrderPaymentResult>
+{
+    private readonly IOrderRepository _orderRepository;
+    private readonly ILogger<CompleteOrderPaymentCommandHandler> _logger;
+
+    public CompleteOrderPaymentCommandHandler(
+        IOrderRepository orderRepository,
+        ILogger<CompleteOrderPaymentCommandHandler> logger)
+    {
+        _orderRepository = orderRepository ?? throw new ArgumentNullException(nameof(orderRepository));
+        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
+    }
+
+    public async Task<CompleteOrderPaymentResult> Handle(
+        CompleteOrderPaymentCommand request,
+        CancellationToken cancellationToken)
+    {
+        _logger.LogInformation(
+            "EN: Completing payment for order {OrderId}, success: {IsSuccess}, gateway txn: {GatewayTxnId} / VI: Hoàn tất thanh toán cho order {OrderId}, thành công: {IsSuccess}, giao dịch gateway: {GatewayTxnId}",
+            request.OrderId, request.IsSuccess, request.GatewayTransactionId);
+
+        // EN: Load order / VI: Load order
+        var order = await _orderRepository.GetByIdAsync(request.OrderId, cancellationToken);
+        if (order == null)
+        {
+            throw new DomainException($"Order not found: {request.OrderId}");
+        }
+
+        // EN: Verify order is in PaymentPending status / VI: Xác minh order đang ở trạng thái PaymentPending
+        if (order.Status != OrderStatus.PaymentPending)
+        {
+            _logger.LogWarning(
+                "EN: Order {OrderId} is not in PaymentPending status (current: {Status}) / VI: Order {OrderId} không ở trạng thái PaymentPending (hiện tại: {Status})",
+                request.OrderId, order.Status.Name);
+
+            return new CompleteOrderPaymentResult(
+                false, order.Status.Name,
+                $"Order is not awaiting payment (current status: {order.Status.Name})");
+        }
+
+        if (!request.IsSuccess)
+        {
+            // EN: Payment failed — cancel the order
+            // VI: Thanh toán thất bại — hủy order
+            order.Cancel($"Payment failed: gateway response code {request.GatewayResponseCode}");
+
+            await _orderRepository.UnitOfWork.SaveEntitiesAsync(cancellationToken);
+
+            _logger.LogWarning(
+                "EN: Payment failed for order {OrderId}, order cancelled / VI: Thanh toán thất bại cho order {OrderId}, order đã hủy",
+                request.OrderId);
+
+            return new CompleteOrderPaymentResult(false, order.Status.Name, "Payment was not successful");
+        }
+
+        // EN: Complete payment and move to processing
+        // VI: Hoàn tất thanh toán và chuyển sang đang xử lý
+        order.CompletePayment(request.GatewayTransactionId);
+        order.MarkAsProcessing();
+
+        await _orderRepository.UnitOfWork.SaveEntitiesAsync(cancellationToken);
+
+        _logger.LogInformation(
+            "EN: Payment completed for order {OrderId}, now processing / VI: Thanh toán hoàn tất cho order {OrderId}, đang xử lý",
+            order.Id);
+
+        return new CompleteOrderPaymentResult(true, order.Status.Name, null);
+    }
+}
--- a/services/order-service-net/src/OrderService.API/Application/Commands/CreateOrderCommandHandler.cs
+++ b/services/order-service-net/src/OrderService.API/Application/Commands/CreateOrderCommandHandler.cs
@@ -2,6 +2,7 @@
 // VI: Handler cho CreateOrderCommand.

 using MediatR;
+using OrderService.API.Hubs;
 using OrderService.Domain.AggregatesModel.OrderAggregate;
 using OrderService.Domain.Strategies;

@@ -15,15 +16,18 @@ public class CreateOrderCommandHandler : IRequestHandler<CreateOrderCommand, Cre
 {
    private readonly IOrderRepository _orderRepository;
    private readonly IEnumerable<ILineItemStrategy> _strategies;
+    private readonly IPosNotificationService _posNotificationService;
    private readonly ILogger<CreateOrderCommandHandler> _logger;

    public CreateOrderCommandHandler(
        IOrderRepository orderRepository,
        IEnumerable<ILineItemStrategy> strategies,
+        IPosNotificationService posNotificationService,
        ILogger<CreateOrderCommandHandler> logger)
    {
        _orderRepository = orderRepository ?? throw new ArgumentNullException(nameof(orderRepository));
        _strategies = strategies ?? throw new ArgumentNullException(nameof(strategies));
+        _posNotificationService = posNotificationService ?? throw new ArgumentNullException(nameof(posNotificationService));
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
    }

@@ -96,6 +100,44 @@ public class CreateOrderCommandHandler : IRequestHandler<CreateOrderCommand, Cre
            "EN: Order created successfully / VI: Tạo order thành công: {OrderId}",
            order.Id);

+        // EN: Send real-time notification to POS/KDS clients
+        // VI: Gửi thông báo real-time đến POS/KDS clients
+        try
+        {
+            var orderNotification = new OrderNotificationDto(
+                OrderId: order.Id,
+                ShopId: order.ShopId,
+                Status: order.Status.Name,
+                Items: order.Items.Select(i => new OrderItemNotificationDto(
+                    ItemId: i.Id,
+                    ProductId: i.ProductId,
+                    ProductName: i.ProductName,
+                    ProductType: i.ProductType,
+                    Quantity: i.Quantity,
+                    UnitPrice: i.UnitPrice,
+                    TotalPrice: i.TotalPrice,
+                    Status: i.Status
+                )).ToList().AsReadOnly(),
+                TotalAmount: order.TotalAmount,
+                CustomerId: order.CustomerId,
+                TableId: order.TableId,
+                CreatedAt: order.CreatedAt,
+                UpdatedAt: order.UpdatedAt
+            );
+
+            await _posNotificationService.NotifyOrderCreatedAsync(
+                order.ShopId, orderNotification, cancellationToken);
+        }
+        catch (Exception ex)
+        {
+            // EN: Don't fail the command if notification fails
+            // VI: Không fail command nếu notification thất bại
+            _logger.LogWarning(ex,
+                "EN: Failed to send POS notification for order {OrderId} / " +
+                "VI: Gửi thông báo POS thất bại cho order {OrderId}",
+                order.Id);
+        }
+
        return new CreateOrderResult(
            order.Id,
            order.TotalAmount,
--- a/services/order-service-net/src/OrderService.API/Application/Commands/PayOrderCommand.cs
+++ b/services/order-service-net/src/OrderService.API/Application/Commands/PayOrderCommand.cs
@@ -1,17 +1,21 @@
-// EN: Command to pay for an order.
-// VI: Command thanh toán order.
+// EN: Command to pay for an order with payment method details.
+// VI: Command thanh toán order với chi tiết phương thức thanh toán.

 using MediatR;

 namespace OrderService.API.Application.Commands;

 /// <summary>
-/// EN: Command to process payment and execute order.
-/// VI: Command xử lý thanh toán và thực thi order.
+/// EN: Command to process payment for an order. Supports cash, card, vnpay, momo.
+/// VI: Command xử lý thanh toán cho order. Hỗ trợ tiền mặt, thẻ, vnpay, momo.
 /// </summary>
 public record PayOrderCommand(
    Guid OrderId,
-    Guid ShopId
+    Guid ShopId,
+    string PaymentMethod,       // EN: "cash", "card", "vnpay", "momo" / VI: "cash", "card", "vnpay", "momo"
+    decimal? AmountTendered,    // EN: For cash payments (amount customer gave) / VI: Cho thanh toán tiền mặt (số tiền khách đưa)
+    string? ReturnUrl,          // EN: For online payments (redirect after payment) / VI: Cho thanh toán trực tuyến (redirect sau thanh toán)
+    string? IpAddress           // EN: For online payments (client IP) / VI: Cho thanh toán trực tuyến (IP client)
 ) : IRequest<PayOrderResult>;

 /// <summary>
@@ -20,5 +24,9 @@ public record PayOrderCommand(
 /// </summary>
 public record PayOrderResult(
    bool Success,
-    string Status
+    string Status,
+    string? PaymentUrl,         // EN: Redirect URL for VNPay/Momo / VI: URL redirect cho VNPay/Momo
+    decimal? ChangeAmount,      // EN: Change for cash payments / VI: Tiền thối cho thanh toán tiền mặt
+    string? TransactionId,      // EN: Transaction ID / VI: Mã giao dịch
+    string? ErrorMessage        // EN: Error message if failed / VI: Thông báo lỗi nếu thất bại
 );
--- a/services/order-service-net/src/OrderService.API/Application/Commands/PayOrderCommandHandler.cs
+++ b/services/order-service-net/src/OrderService.API/Application/Commands/PayOrderCommandHandler.cs
@@ -1,26 +1,34 @@
-// EN: Handler for PayOrderCommand.
-// VI: Handler cho PayOrderCommand.
+// EN: Handler for PayOrderCommand — routes to cash, card, or online payment flow.
+// VI: Handler cho PayOrderCommand — điều hướng đến thanh toán tiền mặt, thẻ, hoặc trực tuyến.

 using MediatR;
+using OrderService.API.Hubs;
 using OrderService.Domain.AggregatesModel.OrderAggregate;
 using OrderService.Domain.Exceptions;
+using OrderService.Infrastructure.ExternalServices;

 namespace OrderService.API.Application.Commands;

 /// <summary>
-/// EN: Handler for processing payment.
-/// VI: Handler xử lý thanh toán.
+/// EN: Handler for processing payment based on payment method.
+/// VI: Handler xử lý thanh toán dựa trên phương thức thanh toán.
 /// </summary>
 public class PayOrderCommandHandler : IRequestHandler<PayOrderCommand, PayOrderResult>
 {
    private readonly IOrderRepository _orderRepository;
+    private readonly IWalletServiceClient _walletServiceClient;
+    private readonly IPosNotificationService _posNotificationService;
    private readonly ILogger<PayOrderCommandHandler> _logger;

    public PayOrderCommandHandler(
        IOrderRepository orderRepository,
+        IWalletServiceClient walletServiceClient,
+        IPosNotificationService posNotificationService,
        ILogger<PayOrderCommandHandler> logger)
    {
        _orderRepository = orderRepository ?? throw new ArgumentNullException(nameof(orderRepository));
+        _walletServiceClient = walletServiceClient ?? throw new ArgumentNullException(nameof(walletServiceClient));
+        _posNotificationService = posNotificationService ?? throw new ArgumentNullException(nameof(posNotificationService));
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
    }

@@ -29,40 +37,181 @@ public class PayOrderCommandHandler : IRequestHandler<PayOrderCommand, PayOrderR
        CancellationToken cancellationToken)
    {
        _logger.LogInformation(
-            "EN: Processing payment for order {OrderId} / VI: Xử lý thanh toán cho order {OrderId}",
-            request.OrderId);
+            "EN: Processing {PaymentMethod} payment for order {OrderId} / VI: Xử lý thanh toán {PaymentMethod} cho order {OrderId}",
+            request.PaymentMethod, request.OrderId);

-        // EN: Load order
-        // VI: Load order
+        // EN: Load order / VI: Load order
        var order = await _orderRepository.GetByIdAsync(request.OrderId, cancellationToken);
        if (order == null)
        {
            throw new DomainException($"Order not found: {request.OrderId}");
        }

-        // EN: Verify shop ownership
-        // VI: Xác minh quyền sở hữu shop
+        // EN: Verify shop ownership / VI: Xác minh quyền sở hữu shop
        if (order.ShopId != request.ShopId)
        {
            throw new DomainException("Order does not belong to this shop");
        }

-        // EN: Mark order as paid (will validate status internally)
-        // VI: Đánh dấu order là đã thanh toán (sẽ validate status bên trong)
-        order.MarkAsPaid();
+        var method = request.PaymentMethod.ToLowerInvariant();

-        // EN: Mark order as processing (strategies already executed at order creation)
-        // VI: Đánh dấu order là đang xử lý (strategies đã được thực thi khi tạo order)
+        return method switch
+        {
+            "cash" => await ProcessCashPayment(order, request, cancellationToken),
+            "card" => await ProcessCardPayment(order, request, cancellationToken),
+            "vnpay" or "momo" => await ProcessOnlinePayment(order, request, method, cancellationToken),
+            // EN: Default — treat "qr" and "transfer" as immediate like card (POS-confirmed)
+            // VI: Mặc định — xử lý "qr" và "transfer" như thẻ (POS xác nhận)
+            _ => await ProcessCardPayment(order, request, cancellationToken),
+        };
+    }
+
+    /// <summary>
+    /// EN: Process cash payment — instant, calculate change.
+    /// VI: Xử lý thanh toán tiền mặt — ngay lập tức, tính tiền thối.
+    /// </summary>
+    private async Task<PayOrderResult> ProcessCashPayment(
+        Order order,
+        PayOrderCommand request,
+        CancellationToken cancellationToken)
+    {
+        var amountTendered = request.AmountTendered ?? order.TotalAmount;
+
+        if (amountTendered < order.TotalAmount)
+        {
+            return new PayOrderResult(
+                false, order.Status.Name, null, null, null,
+                $"Insufficient cash: tendered {amountTendered}, required {order.TotalAmount}");
+        }
+
+        var transactionId = $"CASH-{DateTime.UtcNow:yyyyMMddHHmmss}-{Guid.NewGuid().ToString("N")[..8].ToUpper()}";
+        var changeAmount = amountTendered - order.TotalAmount;
+
+        // EN: Mark as paid and processing / VI: Đánh dấu đã thanh toán và đang xử lý
+        order.MarkAsPaid("cash", transactionId, amountTendered);
        order.MarkAsProcessing();

-        // EN: Save changes
-        // VI: Lưu thay đổi
        await _orderRepository.UnitOfWork.SaveEntitiesAsync(cancellationToken);

        _logger.LogInformation(
-            "EN: Payment processed successfully / VI: Xử lý thanh toán thành công: {OrderId}",
+            "EN: Cash payment completed for order {OrderId}, change: {Change} / VI: Thanh toán tiền mặt hoàn tất cho order {OrderId}, tiền thối: {Change}",
+            order.Id, changeAmount);
+
+        // EN: Send real-time payment notification / VI: Gửi thông báo thanh toán real-time
+        await SendPaymentNotificationAsync(order, "cash", cancellationToken);
+
+        return new PayOrderResult(true, order.Status.Name, null, changeAmount, transactionId, null);
+    }
+
+    /// <summary>
+    /// EN: Process card payment — instant (terminal handles actual charge).
+    /// VI: Xử lý thanh toán thẻ — ngay lập tức (terminal xử lý giao dịch thực).
+    /// </summary>
+    private async Task<PayOrderResult> ProcessCardPayment(
+        Order order,
+        PayOrderCommand request,
+        CancellationToken cancellationToken)
+    {
+        var transactionId = $"CARD-{DateTime.UtcNow:yyyyMMddHHmmss}-{Guid.NewGuid().ToString("N")[..8].ToUpper()}";
+
+        // EN: Mark as paid and processing / VI: Đánh dấu đã thanh toán và đang xử lý
+        order.MarkAsPaid(request.PaymentMethod.ToLowerInvariant(), transactionId);
+        order.MarkAsProcessing();
+
+        await _orderRepository.UnitOfWork.SaveEntitiesAsync(cancellationToken);
+
+        _logger.LogInformation(
+            "EN: Card payment completed for order {OrderId} / VI: Thanh toán thẻ hoàn tất cho order {OrderId}",
            order.Id);

-        return new PayOrderResult(true, order.Status.Name);
+        // EN: Send real-time payment notification / VI: Gửi thông báo thanh toán real-time
+        await SendPaymentNotificationAsync(order, request.PaymentMethod.ToLowerInvariant(), cancellationToken);
+
+        return new PayOrderResult(true, order.Status.Name, null, null, transactionId, null);
+    }
+
+    /// <summary>
+    /// EN: Process online payment (VNPay/Momo) — creates payment via wallet-service, returns redirect URL.
+    /// VI: Xử lý thanh toán trực tuyến (VNPay/Momo) — tạo payment qua wallet-service, trả về URL redirect.
+    /// </summary>
+    private async Task<PayOrderResult> ProcessOnlinePayment(
+        Order order,
+        PayOrderCommand request,
+        string gateway,
+        CancellationToken cancellationToken)
+    {
+        try
+        {
+            var paymentResponse = await _walletServiceClient.CreatePaymentAsync(
+                order.Id,
+                order.TotalAmount,
+                gateway,
+                request.ReturnUrl ?? "",
+                request.IpAddress ?? "127.0.0.1",
+                cancellationToken);
+
+            if (paymentResponse == null || string.IsNullOrEmpty(paymentResponse.PaymentUrl))
+            {
+                return new PayOrderResult(
+                    false, order.Status.Name, null, null, null,
+                    "Failed to create online payment / Không thể tạo thanh toán trực tuyến");
+            }
+
+            // EN: Mark order as payment pending / VI: Đánh dấu order chờ thanh toán
+            order.MarkAsPaymentPending(gateway, paymentResponse.TransactionId);
+
+            await _orderRepository.UnitOfWork.SaveEntitiesAsync(cancellationToken);
+
+            _logger.LogInformation(
+                "EN: Online payment initiated for order {OrderId} via {Gateway}, txn: {TxnId} / VI: Thanh toán trực tuyến đã khởi tạo cho order {OrderId} qua {Gateway}, giao dịch: {TxnId}",
+                order.Id, gateway, paymentResponse.TransactionId);
+
+            return new PayOrderResult(
+                true, order.Status.Name, paymentResponse.PaymentUrl, null, paymentResponse.TransactionId, null);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex,
+                "EN: Failed to create online payment for order {OrderId} / VI: Không thể tạo thanh toán trực tuyến cho order {OrderId}",
+                order.Id);
+
+            return new PayOrderResult(
+                false, order.Status.Name, null, null, null,
+                $"Payment gateway error: {ex.Message}");
+        }
+    }
+
+    /// <summary>
+    /// EN: Send real-time payment notification to POS/KDS clients.
+    /// VI: Gửi thông báo thanh toán real-time đến POS/KDS clients.
+    /// </summary>
+    private async Task SendPaymentNotificationAsync(
+        Order order,
+        string paymentMethod,
+        CancellationToken cancellationToken)
+    {
+        try
+        {
+            var payment = new PaymentNotificationDto(
+                OrderId: order.Id,
+                Amount: order.TotalAmount,
+                Method: paymentMethod,
+                Status: "Completed");
+
+            await _posNotificationService.NotifyPaymentCompletedAsync(
+                order.ShopId, payment, cancellationToken);
+
+            await _posNotificationService.NotifyOrderStatusChangedAsync(
+                order.ShopId, order.Id, "Validated", order.Status.Name, cancellationToken);
+        }
+        catch (Exception ex)
+        {
+            // EN: Don't fail the command if notification fails
+            // VI: Không fail command nếu notification thất bại
+            _logger.LogWarning(ex,
+                "EN: Failed to send payment notification for order {OrderId} / " +
+                "VI: Gửi thông báo thanh toán thất bại cho order {OrderId}",
+                order.Id);
+        }
    }
 }
--- a/services/order-service-net/src/OrderService.API/Application/DTOs/OrderDtos.cs
+++ b/services/order-service-net/src/OrderService.API/Application/DTOs/OrderDtos.cs
@@ -13,6 +13,10 @@ public record OrderDto(
    Guid? CustomerId,
    string Status,
    decimal TotalAmount,
+    string? PaymentMethod,
+    string? TransactionId,
+    decimal? AmountTendered,
+    decimal? ChangeAmount,
    DateTime CreatedAt,
    DateTime? UpdatedAt,
    List<OrderItemDto> Items
--- a/services/order-service-net/src/OrderService.API/Application/Queries/GetOrderByIdQueryHandler.cs
+++ b/services/order-service-net/src/OrderService.API/Application/Queries/GetOrderByIdQueryHandler.cs
@@ -30,12 +30,16 @@ public class GetOrderByIdQueryHandler : IRequestHandler<GetOrderByIdQuery, Order
        CancellationToken cancellationToken)
    {
        const string orderSql = @"
-            SELECT 
+            SELECT
                o.id AS Id,
                o.shop_id AS ShopId,
                o.customer_id AS CustomerId,
                os.name AS Status,
                o.total_amount AS TotalAmount,
+                o.payment_method AS PaymentMethod,
+                o.transaction_id AS TransactionId,
+                o.amount_tendered AS AmountTendered,
+                o.change_amount AS ChangeAmount,
                o.created_at AS CreatedAt,
                o.updated_at AS UpdatedAt
            FROM orders o
@@ -82,6 +86,10 @@ public class GetOrderByIdQueryHandler : IRequestHandler<GetOrderByIdQuery, Order
            order.CustomerId,
            order.Status,
            order.TotalAmount,
+            order.PaymentMethod,
+            order.TransactionId,
+            order.AmountTendered,
+            order.ChangeAmount,
            order.CreatedAt,
            order.UpdatedAt,
            items.ToList()
@@ -96,6 +104,10 @@ public class GetOrderByIdQueryHandler : IRequestHandler<GetOrderByIdQuery, Order
        Guid? CustomerId,
        string Status,
        decimal TotalAmount,
+        string? PaymentMethod,
+        string? TransactionId,
+        decimal? AmountTendered,
+        decimal? ChangeAmount,
        DateTime CreatedAt,
        DateTime? UpdatedAt
    );
--- a/services/order-service-net/src/OrderService.API/Application/Validations/PayOrderCommandValidator.cs
+++ b/services/order-service-net/src/OrderService.API/Application/Validations/PayOrderCommandValidator.cs
@@ -1,16 +1,22 @@
-// EN: Validator for PayOrderCommand.
-// VI: Validator cho PayOrderCommand.
+// EN: Validator for PayOrderCommand with payment method-specific rules.
+// VI: Validator cho PayOrderCommand với quy tắc theo phương thức thanh toán.

 using FluentValidation;

 namespace OrderService.API.Application.Validations;

 /// <summary>
-/// EN: Validator for PayOrderCommand.
-/// VI: Validator cho PayOrderCommand.
+/// EN: Validator for PayOrderCommand — validates payment method and conditional fields.
+/// VI: Validator cho PayOrderCommand — validate phương thức thanh toán và các trường điều kiện.
 /// </summary>
 public class PayOrderCommandValidator : AbstractValidator<Commands.PayOrderCommand>
 {
+    /// <summary>
+    /// EN: Supported payment methods.
+    /// VI: Các phương thức thanh toán được hỗ trợ.
+    /// </summary>
+    private static readonly string[] SupportedMethods = { "cash", "card", "vnpay", "momo", "qr", "transfer" };
+
    public PayOrderCommandValidator()
    {
        RuleFor(x => x.OrderId)
@@ -20,5 +26,30 @@ public class PayOrderCommandValidator : AbstractValidator<Commands.PayOrderComma
        RuleFor(x => x.ShopId)
            .NotEmpty()
            .WithMessage("EN: Shop ID is required / VI: Shop ID là bắt buộc");
+
+        RuleFor(x => x.PaymentMethod)
+            .NotEmpty()
+            .WithMessage("EN: Payment method is required / VI: Phương thức thanh toán là bắt buộc")
+            .Must(m => SupportedMethods.Contains(m?.ToLowerInvariant()))
+            .WithMessage("EN: Payment method must be one of: cash, card, vnpay, momo, qr, transfer / VI: Phương thức thanh toán phải là: cash, card, vnpay, momo, qr, transfer");
+
+        // EN: AmountTendered required for cash payments
+        // VI: Số tiền khách đưa bắt buộc cho thanh toán tiền mặt
+        RuleFor(x => x.AmountTendered)
+            .NotNull()
+            .When(x => x.PaymentMethod?.ToLowerInvariant() == "cash")
+            .WithMessage("EN: Amount tendered is required for cash payments / VI: Số tiền khách đưa là bắt buộc cho thanh toán tiền mặt");
+
+        RuleFor(x => x.AmountTendered)
+            .GreaterThan(0)
+            .When(x => x.AmountTendered.HasValue)
+            .WithMessage("EN: Amount tendered must be greater than 0 / VI: Số tiền khách đưa phải lớn hơn 0");
+
+        // EN: ReturnUrl required for online payment gateways
+        // VI: ReturnUrl bắt buộc cho cổng thanh toán trực tuyến
+        RuleFor(x => x.ReturnUrl)
+            .NotEmpty()
+            .When(x => x.PaymentMethod?.ToLowerInvariant() is "vnpay" or "momo")
+            .WithMessage("EN: Return URL is required for online payments / VI: URL trả về là bắt buộc cho thanh toán trực tuyến");
    }
 }
--- a/services/order-service-net/src/OrderService.API/Controllers/OrdersController.cs
+++ b/services/order-service-net/src/OrderService.API/Controllers/OrdersController.cs
@@ -102,8 +102,8 @@ public class OrdersController : ControllerBase
    }

    /// <summary>
-    /// EN: Process payment for an order.
-    /// VI: Xử lý thanh toán cho order.
+    /// EN: Process payment for an order with payment method details.
+    /// VI: Xử lý thanh toán cho order với chi tiết phương thức thanh toán.
    /// </summary>
    [HttpPost("{id}/pay")]
    [ProducesResponseType(typeof(PayOrderResult), StatusCodes.Status200OK)]
@@ -112,16 +112,62 @@ public class OrdersController : ControllerBase
    public async Task<ActionResult<PayOrderResult>> PayOrder(
        Guid id,
        [FromQuery] Guid shopId,
+        [FromBody] PayOrderRequest? request = null,
        CancellationToken cancellationToken = default)
    {
        _logger.LogInformation(
-            "EN: Processing payment for order {OrderId} / VI: Xử lý thanh toán cho order {OrderId}",
-            id);
+            "EN: Processing {Method} payment for order {OrderId} / VI: Xử lý thanh toán {Method} cho order {OrderId}",
+            request?.PaymentMethod ?? "unknown", id);
+
+        var command = new PayOrderCommand(
+            id,
+            shopId,
+            request?.PaymentMethod ?? "cash",
+            request?.AmountTendered,
+            request?.ReturnUrl,
+            HttpContext.Connection.RemoteIpAddress?.ToString());

-        var command = new PayOrderCommand(id, shopId);
        var result = await _mediator.Send(command, cancellationToken);

-        return Ok(result);
+        if (!result.Success)
+        {
+            return BadRequest(new { success = false, error = new { code = "PAYMENT_FAILED", message = result.ErrorMessage } });
+        }
+
+        return Ok(new { success = true, data = result });
+    }
+
+    /// <summary>
+    /// EN: Payment callback endpoint — called by wallet-service after payment gateway confirms.
+    /// VI: Endpoint callback thanh toán — được gọi bởi wallet-service sau khi cổng thanh toán xác nhận.
+    /// </summary>
+    [HttpPost("{id}/payment-callback")]
+    [ProducesResponseType(typeof(CompleteOrderPaymentResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    public async Task<ActionResult<CompleteOrderPaymentResult>> PaymentCallback(
+        Guid id,
+        [FromBody] PaymentCallbackRequest request,
+        CancellationToken cancellationToken = default)
+    {
+        _logger.LogInformation(
+            "EN: Payment callback for order {OrderId}, success: {IsSuccess} / VI: Callback thanh toán cho order {OrderId}, thành công: {IsSuccess}",
+            id, request.IsSuccess);
+
+        var command = new CompleteOrderPaymentCommand(
+            id,
+            request.GatewayTransactionId,
+            request.IsSuccess,
+            request.GatewayResponseCode);
+
+        var result = await _mediator.Send(command, cancellationToken);
+
+        if (!result.Success)
+        {
+            return BadRequest(new { success = false, error = new { code = "PAYMENT_CALLBACK_FAILED", message = result.ErrorMessage } });
+        }
+
+        return Ok(new { success = true, data = result });
    }

    /// <summary>
@@ -231,3 +277,23 @@ public class OrdersController : ControllerBase
 /// VI: Yêu cầu hủy order.
 /// </summary>
 public record CancelOrderRequest(string Reason);
+
+/// <summary>
+/// EN: Request to pay an order with payment method details.
+/// VI: Yêu cầu thanh toán order với chi tiết phương thức thanh toán.
+/// </summary>
+public record PayOrderRequest(
+    string? PaymentMethod,      // EN: "cash", "card", "vnpay", "momo", "qr", "transfer" / VI: Phương thức thanh toán
+    decimal? AmountTendered,    // EN: For cash payments / VI: Cho thanh toán tiền mặt
+    string? ReturnUrl           // EN: For online payments / VI: Cho thanh toán trực tuyến
+);
+
+/// <summary>
+/// EN: Payment callback request from wallet-service.
+/// VI: Yêu cầu callback thanh toán từ wallet-service.
+/// </summary>
+public record PaymentCallbackRequest(
+    string GatewayTransactionId,
+    bool IsSuccess,
+    string? GatewayResponseCode
+);
--- a/services/order-service-net/src/OrderService.API/Hubs/ClaimsUserIdProvider.cs
+++ b/services/order-service-net/src/OrderService.API/Hubs/ClaimsUserIdProvider.cs
@@ -0,0 +1,28 @@
+// EN: Custom user ID provider for SignalR hub.
+// VI: Custom user ID provider cho SignalR hub.
+
+using System.Security.Claims;
+using Microsoft.AspNetCore.SignalR;
+
+namespace OrderService.API.Hubs;
+
+/// <summary>
+/// EN: Custom user ID provider that extracts user ID from JWT claims.
+/// VI: Custom user ID provider lấy user ID từ JWT claims.
+/// </summary>
+/// <remarks>
+/// EN: Enables targeting specific users across multiple connections/devices.
+/// VI: Cho phép nhắm đến user cụ thể qua nhiều kết nối/thiết bị.
+/// </remarks>
+public class ClaimsUserIdProvider : IUserIdProvider
+{
+    /// <inheritdoc/>
+    public string? GetUserId(HubConnectionContext connection)
+    {
+        // EN: Try to get user ID from standard claim types
+        // VI: Thử lấy user ID từ các claim types chuẩn
+        return connection.User?.FindFirst(ClaimTypes.NameIdentifier)?.Value
+            ?? connection.User?.FindFirst("sub")?.Value
+            ?? connection.User?.FindFirst("user_id")?.Value;
+    }
+}
--- a/services/order-service-net/src/OrderService.API/Hubs/HubDtos.cs
+++ b/services/order-service-net/src/OrderService.API/Hubs/HubDtos.cs
@@ -0,0 +1,91 @@
+// EN: DTOs for real-time POS/KDS hub notifications.
+// VI: DTOs cho thông báo real-time POS/KDS hub.
+
+namespace OrderService.API.Hubs;
+
+/// <summary>
+/// EN: DTO for order notification via SignalR.
+/// VI: DTO cho thông báo order qua SignalR.
+/// </summary>
+public record OrderNotificationDto(
+    Guid OrderId,
+    Guid ShopId,
+    string Status,
+    IReadOnlyCollection<OrderItemNotificationDto> Items,
+    decimal TotalAmount,
+    Guid? CustomerId,
+    Guid? TableId,
+    DateTime CreatedAt,
+    DateTime? UpdatedAt
+);
+
+/// <summary>
+/// EN: DTO for order item in notification.
+/// VI: DTO cho order item trong thông báo.
+/// </summary>
+public record OrderItemNotificationDto(
+    Guid ItemId,
+    Guid ProductId,
+    string ProductName,
+    string ProductType,
+    int Quantity,
+    decimal UnitPrice,
+    decimal TotalPrice,
+    string Status
+);
+
+/// <summary>
+/// EN: DTO for kitchen ticket notification via SignalR.
+/// VI: DTO cho thông báo phiếu bếp qua SignalR.
+/// </summary>
+public record KitchenTicketNotificationDto(
+    Guid TicketId,
+    Guid OrderId,
+    IReadOnlyCollection<KitchenTicketItemDto> Items,
+    int Priority,
+    string Status,
+    DateTime CreatedAt
+);
+
+/// <summary>
+/// EN: DTO for kitchen ticket item.
+/// VI: DTO cho item trong phiếu bếp.
+/// </summary>
+public record KitchenTicketItemDto(
+    Guid ProductId,
+    string ProductName,
+    int Quantity,
+    string? Notes
+);
+
+/// <summary>
+/// EN: DTO for payment notification via SignalR.
+/// VI: DTO cho thông báo thanh toán qua SignalR.
+/// </summary>
+public record PaymentNotificationDto(
+    Guid OrderId,
+    decimal Amount,
+    string Method,
+    string Status
+);
+
+/// <summary>
+/// EN: DTO for table status change notification via SignalR.
+/// VI: DTO cho thông báo thay đổi trạng thái bàn qua SignalR.
+/// </summary>
+public record TableStatusNotificationDto(
+    Guid TableId,
+    string TableName,
+    string Status
+);
+
+/// <summary>
+/// EN: DTO for order status change notification via SignalR.
+/// VI: DTO cho thông báo thay đổi trạng thái order qua SignalR.
+/// </summary>
+public record OrderStatusChangedDto(
+    Guid OrderId,
+    string OldStatus,
+    string NewStatus,
+    DateTime ChangedAt
+);
--- a/services/order-service-net/src/OrderService.API/Hubs/IPosHubClient.cs
+++ b/services/order-service-net/src/OrderService.API/Hubs/IPosHubClient.cs
@@ -0,0 +1,53 @@
+// EN: Strongly-typed client interface for PosHub.
+// VI: Interface client strongly-typed cho PosHub.
+
+namespace OrderService.API.Hubs;
+
+/// <summary>
+/// EN: Strongly-typed SignalR client interface for POS/KDS real-time updates.
+/// VI: Interface SignalR client strongly-typed cho POS/KDS real-time updates.
+/// </summary>
+public interface IPosHubClient
+{
+    /// <summary>
+    /// EN: Notify clients that a new order was created.
+    /// VI: Thông báo clients rằng order mới đã được tạo.
+    /// </summary>
+    Task OrderCreated(OrderNotificationDto order);
+
+    /// <summary>
+    /// EN: Notify clients that an order was updated.
+    /// VI: Thông báo clients rằng order đã được cập nhật.
+    /// </summary>
+    Task OrderUpdated(OrderNotificationDto order);
+
+    /// <summary>
+    /// EN: Notify clients that an order status changed.
+    /// VI: Thông báo clients rằng trạng thái order đã thay đổi.
+    /// </summary>
+    Task OrderStatusChanged(OrderStatusChangedDto statusChange);
+
+    /// <summary>
+    /// EN: Notify KDS clients that a new kitchen ticket was created.
+    /// VI: Thông báo KDS clients rằng phiếu bếp mới đã được tạo.
+    /// </summary>
+    Task KitchenTicketCreated(KitchenTicketNotificationDto ticket);
+
+    /// <summary>
+    /// EN: Notify KDS clients that a kitchen ticket was updated.
+    /// VI: Thông báo KDS clients rằng phiếu bếp đã được cập nhật.
+    /// </summary>
+    Task KitchenTicketUpdated(KitchenTicketNotificationDto ticket);
+
+    /// <summary>
+    /// EN: Notify clients that payment was completed.
+    /// VI: Thông báo clients rằng thanh toán đã hoàn thành.
+    /// </summary>
+    Task PaymentCompleted(PaymentNotificationDto payment);
+
+    /// <summary>
+    /// EN: Notify clients that a table status changed.
+    /// VI: Thông báo clients rằng trạng thái bàn đã thay đổi.
+    /// </summary>
+    Task TableStatusChanged(TableStatusNotificationDto tableStatus);
+}
--- a/services/order-service-net/src/OrderService.API/Hubs/IPosNotificationService.cs
+++ b/services/order-service-net/src/OrderService.API/Hubs/IPosNotificationService.cs
@@ -0,0 +1,53 @@
+// EN: Interface for POS real-time notification service.
+// VI: Interface cho dịch vụ thông báo real-time POS.
+
+namespace OrderService.API.Hubs;
+
+/// <summary>
+/// EN: Service interface for sending real-time notifications to POS/KDS clients.
+/// VI: Interface dịch vụ gửi thông báo real-time đến POS/KDS clients.
+/// </summary>
+public interface IPosNotificationService
+{
+    /// <summary>
+    /// EN: Notify shop group that a new order was created.
+    /// VI: Thông báo group shop rằng order mới đã được tạo.
+    /// </summary>
+    Task NotifyOrderCreatedAsync(Guid shopId, OrderNotificationDto order, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// EN: Notify shop group that an order was updated.
+    /// VI: Thông báo group shop rằng order đã được cập nhật.
+    /// </summary>
+    Task NotifyOrderUpdatedAsync(Guid shopId, OrderNotificationDto order, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// EN: Notify shop group that an order status changed.
+    /// VI: Thông báo group shop rằng trạng thái order đã thay đổi.
+    /// </summary>
+    Task NotifyOrderStatusChangedAsync(Guid shopId, Guid orderId, string oldStatus, string newStatus, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// EN: Notify KDS group that a new kitchen ticket was created.
+    /// VI: Thông báo group KDS rằng phiếu bếp mới đã được tạo.
+    /// </summary>
+    Task NotifyKitchenTicketCreatedAsync(Guid shopId, KitchenTicketNotificationDto ticket, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// EN: Notify KDS group that a kitchen ticket was updated.
+    /// VI: Thông báo group KDS rằng phiếu bếp đã được cập nhật.
+    /// </summary>
+    Task NotifyKitchenTicketUpdatedAsync(Guid shopId, KitchenTicketNotificationDto ticket, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// EN: Notify shop group that payment was completed.
+    /// VI: Thông báo group shop rằng thanh toán đã hoàn thành.
+    /// </summary>
+    Task NotifyPaymentCompletedAsync(Guid shopId, PaymentNotificationDto payment, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// EN: Notify shop group that a table status changed.
+    /// VI: Thông báo group shop rằng trạng thái bàn đã thay đổi.
+    /// </summary>
+    Task NotifyTableStatusChangedAsync(Guid shopId, TableStatusNotificationDto tableStatus, CancellationToken cancellationToken = default);
+}
--- a/services/order-service-net/src/OrderService.API/Hubs/PosConnectionManager.cs
+++ b/services/order-service-net/src/OrderService.API/Hubs/PosConnectionManager.cs
@@ -0,0 +1,92 @@
+// EN: Connection manager for POS hub - tracks connected users per shop.
+// VI: Connection manager cho POS hub - theo dõi users kết nối theo shop.
+
+using System.Collections.Concurrent;
+
+namespace OrderService.API.Hubs;
+
+/// <summary>
+/// EN: Thread-safe connection manager for POS/KDS hub connections.
+/// VI: Connection manager thread-safe cho POS/KDS hub connections.
+/// </summary>
+public class PosConnectionManager
+{
+    // EN: Maps ConnectionId -> ShopId for quick lookup on disconnect
+    // VI: Maps ConnectionId -> ShopId để tra cứu nhanh khi disconnect
+    private readonly ConcurrentDictionary<string, Guid> _connectionToShop = new();
+
+    // EN: Maps ShopId -> Set of ConnectionIds for shop-level queries
+    // VI: Maps ShopId -> Set ConnectionIds cho truy vấn cấp shop
+    private readonly ConcurrentDictionary<Guid, ConcurrentDictionary<string, byte>> _shopConnections = new();
+
+    /// <summary>
+    /// EN: Register a connection for a shop.
+    /// VI: Đăng ký kết nối cho shop.
+    /// </summary>
+    public void AddConnection(string connectionId, Guid shopId)
+    {
+        _connectionToShop[connectionId] = shopId;
+
+        var connections = _shopConnections.GetOrAdd(shopId, _ => new ConcurrentDictionary<string, byte>());
+        connections[connectionId] = 0;
+    }
+
+    /// <summary>
+    /// EN: Remove a connection and return the associated shop ID.
+    /// VI: Xóa kết nối và trả về shop ID liên kết.
+    /// </summary>
+    public Guid? RemoveConnection(string connectionId)
+    {
+        if (!_connectionToShop.TryRemove(connectionId, out var shopId))
+        {
+            return null;
+        }
+
+        if (_shopConnections.TryGetValue(shopId, out var connections))
+        {
+            connections.TryRemove(connectionId, out _);
+
+            // EN: Clean up empty shop entries / VI: Dọn dẹp các shop không còn kết nối
+            if (connections.IsEmpty)
+            {
+                _shopConnections.TryRemove(shopId, out _);
+            }
+        }
+
+        return shopId;
+    }
+
+    /// <summary>
+    /// EN: Get all connection IDs for a specific shop.
+    /// VI: Lấy tất cả connection IDs cho shop cụ thể.
+    /// </summary>
+    public IReadOnlyCollection<string> GetShopConnections(Guid shopId)
+    {
+        if (_shopConnections.TryGetValue(shopId, out var connections))
+        {
+            return connections.Keys.ToList().AsReadOnly();
+        }
+
+        return Array.Empty<string>();
+    }
+
+    /// <summary>
+    /// EN: Get the number of active connections for a shop.
+    /// VI: Lấy số lượng kết nối active cho shop.
+    /// </summary>
+    public int GetShopConnectionCount(Guid shopId)
+    {
+        if (_shopConnections.TryGetValue(shopId, out var connections))
+        {
+            return connections.Count;
+        }
+
+        return 0;
+    }
+
+    /// <summary>
+    /// EN: Get total number of active connections.
+    /// VI: Lấy tổng số kết nối active.
+    /// </summary>
+    public int TotalConnections => _connectionToShop.Count;
+}
--- a/services/order-service-net/src/OrderService.API/Hubs/PosHub.cs
+++ b/services/order-service-net/src/OrderService.API/Hubs/PosHub.cs
@@ -0,0 +1,203 @@
+// EN: Real-time SignalR hub for POS and KDS updates.
+// VI: SignalR hub thời gian thực cho POS và KDS.
+
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.SignalR;
+
+namespace OrderService.API.Hubs;
+
+/// <summary>
+/// EN: Real-time SignalR hub for POS and KDS updates.
+/// VI: SignalR hub thời gian thực cho POS và KDS.
+/// </summary>
+/// <remarks>
+/// EN: Group naming convention:
+///   - shop:{shopId} — all POS updates for a shop
+///   - kds:{shopId}  — kitchen display system updates only
+///   - pos:{shopId}  — POS terminal updates only
+/// VI: Quy ước đặt tên group:
+///   - shop:{shopId} — tất cả cập nhật POS cho shop
+///   - kds:{shopId}  — chỉ cập nhật hệ thống hiển thị bếp
+///   - pos:{shopId}  — chỉ cập nhật thiết bị POS
+/// </remarks>
+[Authorize]
+public class PosHub : Hub<IPosHubClient>
+{
+    private readonly PosConnectionManager _connectionManager;
+    private readonly ILogger<PosHub> _logger;
+
+    public PosHub(
+        PosConnectionManager connectionManager,
+        ILogger<PosHub> logger)
+    {
+        _connectionManager = connectionManager;
+        _logger = logger;
+    }
+
+    #region Connection Lifecycle
+
+    /// <summary>
+    /// EN: Called when a new connection is established.
+    /// VI: Được gọi khi kết nối mới được thiết lập.
+    /// </summary>
+    public override async Task OnConnectedAsync()
+    {
+        var userId = Context.UserIdentifier;
+        if (string.IsNullOrEmpty(userId))
+        {
+            _logger.LogWarning(
+                "EN: POS hub connection attempted without user identifier / " +
+                "VI: POS hub kết nối mà không có user identifier");
+            await base.OnConnectedAsync();
+            return;
+        }
+
+        _logger.LogInformation(
+            "EN: User {UserId} connected to POS hub with connection {ConnectionId} / " +
+            "VI: User {UserId} kết nối POS hub với connection {ConnectionId}",
+            userId, Context.ConnectionId);
+
+        await base.OnConnectedAsync();
+    }
+
+    /// <summary>
+    /// EN: Called when a connection is terminated.
+    /// VI: Được gọi khi kết nối bị ngắt.
+    /// </summary>
+    public override async Task OnDisconnectedAsync(Exception? exception)
+    {
+        var shopId = _connectionManager.RemoveConnection(Context.ConnectionId);
+
+        if (shopId.HasValue)
+        {
+            _logger.LogInformation(
+                "EN: Connection {ConnectionId} disconnected from shop {ShopId} / " +
+                "VI: Connection {ConnectionId} ngắt kết nối khỏi shop {ShopId}",
+                Context.ConnectionId, shopId.Value);
+        }
+
+        if (exception != null)
+        {
+            _logger.LogError(exception,
+                "EN: POS hub connection {ConnectionId} disconnected with error / " +
+                "VI: POS hub connection {ConnectionId} ngắt kết nối với lỗi",
+                Context.ConnectionId);
+        }
+
+        await base.OnDisconnectedAsync(exception);
+    }
+
+    #endregion
+
+    #region Group Management
+
+    /// <summary>
+    /// EN: Join a shop group to receive all POS updates for that shop.
+    /// VI: Tham gia group shop để nhận tất cả cập nhật POS cho shop đó.
+    /// </summary>
+    public async Task JoinShop(Guid shopId)
+    {
+        var userId = Context.UserIdentifier
+            ?? throw new HubException("User not authenticated / User chưa xác thực");
+
+        _logger.LogInformation(
+            "EN: User {UserId} joining shop {ShopId} / " +
+            "VI: User {UserId} tham gia shop {ShopId}",
+            userId, shopId);
+
+        _connectionManager.AddConnection(Context.ConnectionId, shopId);
+
+        await Groups.AddToGroupAsync(Context.ConnectionId, $"shop:{shopId}");
+    }
+
+    /// <summary>
+    /// EN: Join a KDS group to receive kitchen updates only.
+    /// VI: Tham gia group KDS để nhận cập nhật bếp.
+    /// </summary>
+    public async Task JoinKds(Guid shopId)
+    {
+        var userId = Context.UserIdentifier
+            ?? throw new HubException("User not authenticated / User chưa xác thực");
+
+        _logger.LogInformation(
+            "EN: User {UserId} joining KDS for shop {ShopId} / " +
+            "VI: User {UserId} tham gia KDS cho shop {ShopId}",
+            userId, shopId);
+
+        _connectionManager.AddConnection(Context.ConnectionId, shopId);
+
+        await Groups.AddToGroupAsync(Context.ConnectionId, $"kds:{shopId}");
+    }
+
+    /// <summary>
+    /// EN: Join a POS terminal group.
+    /// VI: Tham gia group thiết bị POS.
+    /// </summary>
+    public async Task JoinPos(Guid shopId)
+    {
+        var userId = Context.UserIdentifier
+            ?? throw new HubException("User not authenticated / User chưa xác thực");
+
+        _logger.LogInformation(
+            "EN: User {UserId} joining POS terminal for shop {ShopId} / " +
+            "VI: User {UserId} tham gia thiết bị POS cho shop {ShopId}",
+            userId, shopId);
+
+        _connectionManager.AddConnection(Context.ConnectionId, shopId);
+
+        await Groups.AddToGroupAsync(Context.ConnectionId, $"pos:{shopId}");
+    }
+
+    /// <summary>
+    /// EN: Leave a shop group.
+    /// VI: Rời group shop.
+    /// </summary>
+    public async Task LeaveShop(Guid shopId)
+    {
+        var userId = Context.UserIdentifier
+            ?? throw new HubException("User not authenticated / User chưa xác thực");
+
+        _logger.LogInformation(
+            "EN: User {UserId} leaving shop {ShopId} / " +
+            "VI: User {UserId} rời shop {ShopId}",
+            userId, shopId);
+
+        await Groups.RemoveFromGroupAsync(Context.ConnectionId, $"shop:{shopId}");
+    }
+
+    /// <summary>
+    /// EN: Leave a KDS group.
+    /// VI: Rời group KDS.
+    /// </summary>
+    public async Task LeaveKds(Guid shopId)
+    {
+        var userId = Context.UserIdentifier
+            ?? throw new HubException("User not authenticated / User chưa xác thực");
+
+        _logger.LogInformation(
+            "EN: User {UserId} leaving KDS for shop {ShopId} / " +
+            "VI: User {UserId} rời KDS cho shop {ShopId}",
+            userId, shopId);
+
+        await Groups.RemoveFromGroupAsync(Context.ConnectionId, $"kds:{shopId}");
+    }
+
+    /// <summary>
+    /// EN: Leave a POS terminal group.
+    /// VI: Rời group thiết bị POS.
+    /// </summary>
+    public async Task LeavePos(Guid shopId)
+    {
+        var userId = Context.UserIdentifier
+            ?? throw new HubException("User not authenticated / User chưa xác thực");
+
+        _logger.LogInformation(
+            "EN: User {UserId} leaving POS terminal for shop {ShopId} / " +
+            "VI: User {UserId} rời thiết bị POS cho shop {ShopId}",
+            userId, shopId);
+
+        await Groups.RemoveFromGroupAsync(Context.ConnectionId, $"pos:{shopId}");
+    }
+
+    #endregion
+}
--- a/services/order-service-net/src/OrderService.API/Hubs/PosNotificationService.cs
+++ b/services/order-service-net/src/OrderService.API/Hubs/PosNotificationService.cs
@@ -0,0 +1,155 @@
+// EN: Implementation of POS real-time notification service using SignalR.
+// VI: Implementation dịch vụ thông báo real-time POS sử dụng SignalR.
+
+using Microsoft.AspNetCore.SignalR;
+
+namespace OrderService.API.Hubs;
+
+/// <summary>
+/// EN: Sends real-time notifications to POS/KDS clients via SignalR hub context.
+/// VI: Gửi thông báo real-time đến POS/KDS clients qua SignalR hub context.
+/// </summary>
+public class PosNotificationService : IPosNotificationService
+{
+    private readonly IHubContext<PosHub, IPosHubClient> _hubContext;
+    private readonly ILogger<PosNotificationService> _logger;
+
+    public PosNotificationService(
+        IHubContext<PosHub, IPosHubClient> hubContext,
+        ILogger<PosNotificationService> logger)
+    {
+        _hubContext = hubContext ?? throw new ArgumentNullException(nameof(hubContext));
+        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
+    }
+
+    /// <inheritdoc/>
+    public async Task NotifyOrderCreatedAsync(
+        Guid shopId,
+        OrderNotificationDto order,
+        CancellationToken cancellationToken = default)
+    {
+        _logger.LogInformation(
+            "EN: Sending OrderCreated notification for order {OrderId} to shop {ShopId} / " +
+            "VI: Gửi thông báo OrderCreated cho order {OrderId} đến shop {ShopId}",
+            order.OrderId, shopId);
+
+        // EN: Send to both shop and pos groups / VI: Gửi đến cả group shop và pos
+        await Task.WhenAll(
+            _hubContext.Clients.Group($"shop:{shopId}").OrderCreated(order),
+            _hubContext.Clients.Group($"pos:{shopId}").OrderCreated(order)
+        );
+    }
+
+    /// <inheritdoc/>
+    public async Task NotifyOrderUpdatedAsync(
+        Guid shopId,
+        OrderNotificationDto order,
+        CancellationToken cancellationToken = default)
+    {
+        _logger.LogInformation(
+            "EN: Sending OrderUpdated notification for order {OrderId} to shop {ShopId} / " +
+            "VI: Gửi thông báo OrderUpdated cho order {OrderId} đến shop {ShopId}",
+            order.OrderId, shopId);
+
+        await _hubContext.Clients.Group($"shop:{shopId}").OrderUpdated(order);
+    }
+
+    /// <inheritdoc/>
+    public async Task NotifyOrderStatusChangedAsync(
+        Guid shopId,
+        Guid orderId,
+        string oldStatus,
+        string newStatus,
+        CancellationToken cancellationToken = default)
+    {
+        _logger.LogInformation(
+            "EN: Sending OrderStatusChanged notification for order {OrderId}: {OldStatus} -> {NewStatus} / " +
+            "VI: Gửi thông báo OrderStatusChanged cho order {OrderId}: {OldStatus} -> {NewStatus}",
+            orderId, oldStatus, newStatus);
+
+        var statusChange = new OrderStatusChangedDto(
+            orderId,
+            oldStatus,
+            newStatus,
+            DateTime.UtcNow);
+
+        // EN: Send to all groups (shop, pos, kds) / VI: Gửi đến tất cả groups (shop, pos, kds)
+        await Task.WhenAll(
+            _hubContext.Clients.Group($"shop:{shopId}").OrderStatusChanged(statusChange),
+            _hubContext.Clients.Group($"pos:{shopId}").OrderStatusChanged(statusChange),
+            _hubContext.Clients.Group($"kds:{shopId}").OrderStatusChanged(statusChange)
+        );
+    }
+
+    /// <inheritdoc/>
+    public async Task NotifyKitchenTicketCreatedAsync(
+        Guid shopId,
+        KitchenTicketNotificationDto ticket,
+        CancellationToken cancellationToken = default)
+    {
+        _logger.LogInformation(
+            "EN: Sending KitchenTicketCreated notification for ticket {TicketId} to KDS shop {ShopId} / " +
+            "VI: Gửi thông báo KitchenTicketCreated cho phiếu {TicketId} đến KDS shop {ShopId}",
+            ticket.TicketId, shopId);
+
+        // EN: Send to both shop and kds groups / VI: Gửi đến cả group shop và kds
+        await Task.WhenAll(
+            _hubContext.Clients.Group($"shop:{shopId}").KitchenTicketCreated(ticket),
+            _hubContext.Clients.Group($"kds:{shopId}").KitchenTicketCreated(ticket)
+        );
+    }
+
+    /// <inheritdoc/>
+    public async Task NotifyKitchenTicketUpdatedAsync(
+        Guid shopId,
+        KitchenTicketNotificationDto ticket,
+        CancellationToken cancellationToken = default)
+    {
+        _logger.LogInformation(
+            "EN: Sending KitchenTicketUpdated notification for ticket {TicketId} to KDS shop {ShopId} / " +
+            "VI: Gửi thông báo KitchenTicketUpdated cho phiếu {TicketId} đến KDS shop {ShopId}",
+            ticket.TicketId, shopId);
+
+        await Task.WhenAll(
+            _hubContext.Clients.Group($"shop:{shopId}").KitchenTicketUpdated(ticket),
+            _hubContext.Clients.Group($"kds:{shopId}").KitchenTicketUpdated(ticket)
+        );
+    }
+
+    /// <inheritdoc/>
+    public async Task NotifyPaymentCompletedAsync(
+        Guid shopId,
+        PaymentNotificationDto payment,
+        CancellationToken cancellationToken = default)
+    {
+        _logger.LogInformation(
+            "EN: Sending PaymentCompleted notification for order {OrderId} to shop {ShopId} / " +
+            "VI: Gửi thông báo PaymentCompleted cho order {OrderId} đến shop {ShopId}",
+            payment.OrderId, shopId);
+
+        // EN: Send to both shop and pos groups / VI: Gửi đến cả group shop và pos
+        await Task.WhenAll(
+            _hubContext.Clients.Group($"shop:{shopId}").PaymentCompleted(payment),
+            _hubContext.Clients.Group($"pos:{shopId}").PaymentCompleted(payment)
+        );
+    }
+
+    /// <inheritdoc/>
+    public async Task NotifyTableStatusChangedAsync(
+        Guid shopId,
+        TableStatusNotificationDto tableStatus,
+        CancellationToken cancellationToken = default)
+    {
+        _logger.LogInformation(
+            "EN: Sending TableStatusChanged notification for table {TableId} to shop {ShopId} / " +
+            "VI: Gửi thông báo TableStatusChanged cho bàn {TableId} đến shop {ShopId}",
+            tableStatus.TableId, shopId);
+
+        // EN: Send to all groups / VI: Gửi đến tất cả groups
+        await Task.WhenAll(
+            _hubContext.Clients.Group($"shop:{shopId}").TableStatusChanged(tableStatus),
+            _hubContext.Clients.Group($"pos:{shopId}").TableStatusChanged(tableStatus),
+            _hubContext.Clients.Group($"kds:{shopId}").TableStatusChanged(tableStatus)
+        );
+    }
+}
--- a/services/order-service-net/src/OrderService.API/OrderService.API.csproj
+++ b/services/order-service-net/src/OrderService.API/OrderService.API.csproj
@@ -36,6 +36,10 @@
    <PackageReference Include="Serilog.AspNetCore" Version="8.0.3" />
    <PackageReference Include="Serilog.Sinks.Console" Version="6.0.0" />
    <PackageReference Include="Serilog.Sinks.Seq" Version="8.0.0" />
+
+    <!-- EN: SignalR for real-time POS/KDS communication / VI: SignalR cho real-time POS/KDS -->
+    <PackageReference Include="Microsoft.AspNetCore.SignalR.StackExchangeRedis" Version="9.0.0" />
+    <PackageReference Include="Microsoft.AspNetCore.SignalR.Protocols.MessagePack" Version="9.0.0" />
  </ItemGroup>

  <ItemGroup>
--- a/services/order-service-net/src/OrderService.API/Program.cs
+++ b/services/order-service-net/src/OrderService.API/Program.cs
@@ -2,15 +2,18 @@ using Microsoft.EntityFrameworkCore;
 using System.Data;
 using FluentValidation;
 using Hellang.Middleware.ProblemDetails;
+using Microsoft.AspNetCore.SignalR;
 using Npgsql;
 using OrderService.API.Application.Behaviors;
 using OrderService.API.Application.Strategies;
+using OrderService.API.Hubs;
 using OrderService.API.Infrastructure.HttpClients;
 using OrderService.Domain.Strategies;
 using OrderService.Infrastructure;
 using Polly;
 using Polly.Extensions.Http;
 using Serilog;
+using StackExchange.Redis;

 // EN: Configure Serilog early / VI: Cấu hình Serilog sớm
 Log.Logger = new LoggerConfiguration()
@@ -83,6 +86,14 @@ try
        .AddPolicyHandler(retryPolicy)
        .AddPolicyHandler(circuitBreakerPolicy);

+    builder.Services.AddHttpClient<OrderService.Infrastructure.ExternalServices.WalletServiceClient>(client =>
+        {
+            client.BaseAddress = new Uri(builder.Configuration["Services:WalletService"] ?? "http://wallet-service-net:8080");
+            client.Timeout = TimeSpan.FromSeconds(15);
+        })
+        .AddPolicyHandler(retryPolicy)
+        .AddPolicyHandler(circuitBreakerPolicy);
+
    // EN: Register Strategies / VI: Đăng ký Strategies
    builder.Services.AddTransient<ILineItemStrategy, RetailStrategy>();
    builder.Services.AddTransient<ILineItemStrategy, ServiceStrategy>();
@@ -101,6 +112,45 @@ try
    // EN: Add FluentValidation / VI: Thêm FluentValidation
    builder.Services.AddValidatorsFromAssemblyContaining<Program>();

+    // EN: Add SignalR with Redis Backplane and MessagePack for POS/KDS real-time updates
+    // VI: Thêm SignalR với Redis Backplane và MessagePack cho POS/KDS real-time updates
+    var redisConnection = builder.Configuration.GetConnectionString("Redis")
+        ?? builder.Configuration["Redis:ConnectionString"]
+        ?? "localhost:6379";
+    var signalRBuilder = builder.Services.AddSignalR(options =>
+    {
+        options.EnableDetailedErrors = builder.Environment.IsDevelopment();
+        options.KeepAliveInterval = TimeSpan.FromSeconds(
+            builder.Configuration.GetValue("SignalR:KeepAliveInterval", 15));
+        options.ClientTimeoutInterval = TimeSpan.FromSeconds(
+            builder.Configuration.GetValue("SignalR:ClientTimeoutInterval", 30));
+
+        // EN: Enable Stateful Reconnect (.NET 8+) / VI: Bật Stateful Reconnect
+        options.StatefulReconnectBufferSize =
+            builder.Configuration.GetValue("SignalR:StatefulReconnectBufferSize", 32768);
+    });
+
+    // EN: Add Redis Backplane for scaling / VI: Thêm Redis Backplane để scale
+    signalRBuilder.AddStackExchangeRedis(redisConnection, options =>
+    {
+        options.Configuration.ChannelPrefix = RedisChannel.Literal("OrderService");
+        options.Configuration.AbortOnConnectFail = false;
+    });
+
+    // EN: Add MessagePack protocol for better performance / VI: Thêm MessagePack cho hiệu năng tốt hơn
+    if (builder.Configuration.GetValue("SignalR:EnableMessagePack", true))
+    {
+        signalRBuilder.AddMessagePackProtocol();
+    }
+
+    // EN: Add custom User ID provider / VI: Thêm custom User ID provider
+    builder.Services.AddSingleton<IUserIdProvider, ClaimsUserIdProvider>();
+
+    // EN: Register POS notification service and connection manager
+    // VI: Đăng ký POS notification service và connection manager
+    builder.Services.AddSingleton<PosConnectionManager>();
+    builder.Services.AddScoped<IPosNotificationService, PosNotificationService>();
+
    // EN: Add controllers / VI: Thêm controllers
    builder.Services.AddControllers();

@@ -130,7 +180,11 @@ try
                ?? builder.Configuration["DATABASE_URL"]
                ?? "",
            name: "postgresql",
-            tags: ["db", "postgresql"]);
+            tags: ["db", "postgresql"])
+        .AddRedis(
+            redisConnection,
+            name: "redis",
+            tags: ["cache", "redis"]);

    // EN: Add JWT Bearer authentication via IAM IdentityServer OIDC discovery
    // VI: Thêm JWT Bearer authentication qua IAM IdentityServer OIDC discovery
@@ -146,17 +200,37 @@ try
                ValidateAudience = false,
                ValidateLifetime = true,
            };
+
+            // EN: Allow SignalR to receive JWT from query string (WebSocket can't use headers)
+            // VI: Cho phép SignalR nhận JWT từ query string (WebSocket không thể dùng headers)
+            options.Events = new Microsoft.AspNetCore.Authentication.JwtBearer.JwtBearerEvents
+            {
+                OnMessageReceived = context =>
+                {
+                    var accessToken = context.Request.Query["access_token"];
+                    var path = context.HttpContext.Request.Path;
+                    if (!string.IsNullOrEmpty(accessToken) && path.StartsWithSegments("/hubs"))
+                    {
+                        context.Token = accessToken;
+                    }
+                    return Task.CompletedTask;
+                }
+            };
        });
    builder.Services.AddAuthorization();

-    // EN: Add CORS / VI: Thêm CORS
+    // EN: Add CORS (AllowCredentials required for SignalR WebSocket)
+    // VI: Thêm CORS (AllowCredentials bắt buộc cho SignalR WebSocket)
    builder.Services.AddCors(options =>
    {
        options.AddDefaultPolicy(policy =>
        {
-            policy.AllowAnyOrigin()
+            policy.WithOrigins(
+                    builder.Configuration.GetSection("AllowedOrigins").Get<string[]>()
+                    ?? ["http://localhost:3000", "http://localhost:5173", "http://localhost:5000"])
                  .AllowAnyMethod()
-                  .AllowAnyHeader();
+                  .AllowAnyHeader()
+                  .AllowCredentials(); // EN: Required for SignalR / VI: Bắt buộc cho SignalR
        });
    });

@@ -192,6 +266,12 @@ try
    // EN: Map controllers / VI: Map controllers
    app.MapControllers();

+    // EN: Map SignalR POS Hub / VI: Map SignalR POS Hub
+    app.MapHub<PosHub>("/hubs/pos", options =>
+    {
+        options.AllowStatefulReconnects = true;
+    });
+
    // EN: Run the application / VI: Chạy ứng dụng
    // EN: Auto-apply EF Core migrations on startup
    // VI: Tự động áp dụng EF Core migrations khi khởi động
--- a/services/order-service-net/src/OrderService.API/appsettings.json
+++ b/services/order-service-net/src/OrderService.API/appsettings.json
@@ -35,6 +35,17 @@
    "Redis": {
        "ConnectionString": "localhost:6379"
    },
+    "SignalR": {
+        "KeepAliveInterval": 15,
+        "ClientTimeoutInterval": 30,
+        "StatefulReconnectBufferSize": 32768,
+        "EnableMessagePack": true
+    },
+    "AllowedOrigins": [
+        "http://localhost:3000",
+        "http://localhost:5173",
+        "http://localhost:5000"
+    ],
    "Jwt": {
        "Secret": "your-super-secret-key-min-32-characters",
        "Issuer": "goodgo-platform",
@@ -42,5 +53,8 @@
        "AccessTokenExpiryMinutes": 15,
        "RefreshTokenExpiryDays": 7
    },
+    "Services": {
+        "WalletService": "http://wallet-service-net:8080"
+    },
    "AllowedHosts": "*"
 }
--- a/services/order-service-net/src/OrderService.Domain/AggregatesModel/OrderAggregate/Order.cs
+++ b/services/order-service-net/src/OrderService.Domain/AggregatesModel/OrderAggregate/Order.cs
@@ -25,6 +25,11 @@ public class Order : Entity, IAggregateRoot
    private string? _discountType;
    private string? _discountReference;

+    private string? _paymentMethod;
+    private string? _transactionId;
+    private decimal? _amountTendered;
+    private decimal? _changeAmount;
+
    private readonly List<OrderItem> _items = new();

    /// <summary>
@@ -71,6 +76,30 @@ public class Order : Entity, IAggregateRoot
    public string? DiscountType => _discountType;
    public string? DiscountReference => _discountReference;

+    /// <summary>
+    /// EN: Payment method used (cash, card, vnpay, momo).
+    /// VI: Phương thức thanh toán đã dùng (cash, card, vnpay, momo).
+    /// </summary>
+    public string? PaymentMethod => _paymentMethod;
+
+    /// <summary>
+    /// EN: External transaction ID from payment gateway or generated for cash/card.
+    /// VI: Mã giao dịch bên ngoài từ cổng thanh toán hoặc tạo cho tiền mặt/thẻ.
+    /// </summary>
+    public string? TransactionId => _transactionId;
+
+    /// <summary>
+    /// EN: Amount tendered by customer (for cash payments).
+    /// VI: Số tiền khách đưa (cho thanh toán tiền mặt).
+    /// </summary>
+    public decimal? AmountTendered => _amountTendered;
+
+    /// <summary>
+    /// EN: Change returned to customer (for cash payments).
+    /// VI: Tiền thối lại cho khách (cho thanh toán tiền mặt).
+    /// </summary>
+    public decimal? ChangeAmount => _changeAmount;
+
    public IReadOnlyCollection<OrderItem> Items => _items.AsReadOnly();

    /// <summary>
@@ -145,14 +174,55 @@ public class Order : Entity, IAggregateRoot
    }

    /// <summary>
-    /// EN: Mark order as paid.
-    /// VI: Đánh dấu đơn hàng đã thanh toán.
+    /// EN: Mark order as paid with payment details.
+    /// VI: Đánh dấu đơn hàng đã thanh toán với chi tiết thanh toán.
    /// </summary>
-    public void MarkAsPaid()
+    public void MarkAsPaid(string paymentMethod, string transactionId, decimal? amountTendered = null)
    {
-        if (Status != OrderStatus.Validated)
+        if (Status != OrderStatus.Validated && Status != OrderStatus.PaymentPending)
            throw new DomainException($"Cannot mark as paid order with status {Status.Name}");

+        _paymentMethod = paymentMethod;
+        _transactionId = transactionId;
+        _amountTendered = amountTendered;
+        if (amountTendered.HasValue)
+            _changeAmount = amountTendered.Value - _totalAmount;
+
+        _status = OrderStatus.Paid;
+        StatusId = OrderStatus.Paid.Id;
+        _updatedAt = DateTime.UtcNow;
+
+        AddDomainEvent(new OrderPaidDomainEvent(this));
+    }
+
+    /// <summary>
+    /// EN: Mark order as payment pending (waiting for online payment gateway confirmation).
+    /// VI: Đánh dấu đơn hàng chờ thanh toán (đang chờ xác nhận từ cổng thanh toán trực tuyến).
+    /// </summary>
+    public void MarkAsPaymentPending(string paymentMethod, string transactionId)
+    {
+        if (Status != OrderStatus.Validated)
+            throw new DomainException($"Cannot mark as payment pending order with status {Status.Name}");
+
+        _paymentMethod = paymentMethod;
+        _transactionId = transactionId;
+        _status = OrderStatus.PaymentPending;
+        StatusId = OrderStatus.PaymentPending.Id;
+        _updatedAt = DateTime.UtcNow;
+
+        AddDomainEvent(new OrderPaymentPendingDomainEvent(this));
+    }
+
+    /// <summary>
+    /// EN: Complete payment after gateway confirmation (transitions from PaymentPending to Paid).
+    /// VI: Hoàn tất thanh toán sau xác nhận cổng thanh toán (chuyển từ PaymentPending sang Paid).
+    /// </summary>
+    public void CompletePayment(string gatewayTransactionId)
+    {
+        if (Status != OrderStatus.PaymentPending)
+            throw new DomainException($"Cannot complete payment for order with status {Status.Name}");
+
+        _transactionId = gatewayTransactionId;
        _status = OrderStatus.Paid;
        StatusId = OrderStatus.Paid.Id;
        _updatedAt = DateTime.UtcNow;
--- a/services/order-service-net/src/OrderService.Domain/AggregatesModel/OrderAggregate/OrderStatus.cs
+++ b/services/order-service-net/src/OrderService.Domain/AggregatesModel/OrderAggregate/OrderStatus.cs
@@ -47,6 +47,12 @@ public class OrderStatus : Enumeration
    /// </summary>
    public static readonly OrderStatus Cancelled = new(6, nameof(Cancelled));

+    /// <summary>
+    /// EN: Payment pending — waiting for online payment gateway confirmation (VNPay/Momo).
+    /// VI: Chờ thanh toán — đang chờ xác nhận từ cổng thanh toán trực tuyến (VNPay/Momo).
+    /// </summary>
+    public static readonly OrderStatus PaymentPending = new(7, nameof(PaymentPending));
+
    public OrderStatus(int id, string name) : base(id, name)
    {
    }
--- a/services/order-service-net/src/OrderService.Domain/Events/OrderDomainEvents.cs
+++ b/services/order-service-net/src/OrderService.Domain/Events/OrderDomainEvents.cs
@@ -24,6 +24,12 @@ public record OrderPaidDomainEvent(Order Order) : INotification;
 /// </summary>
 public record OrderCompletedDomainEvent(Order Order) : INotification;

+/// <summary>
+/// EN: Domain event raised when an order is waiting for online payment confirmation.
+/// VI: Domain event phát ra khi đơn hàng đang chờ xác nhận thanh toán trực tuyến.
+/// </summary>
+public record OrderPaymentPendingDomainEvent(Order Order) : INotification;
+
 /// <summary>
 /// EN: Domain event raised when an order is cancelled.
 /// VI: Domain event phát ra khi đơn hàng bị hủy.
--- a/services/order-service-net/src/OrderService.Infrastructure/DependencyInjection.cs
+++ b/services/order-service-net/src/OrderService.Infrastructure/DependencyInjection.cs
@@ -2,6 +2,7 @@ using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
 using OrderService.Domain.AggregatesModel.OrderAggregate;
+using OrderService.Infrastructure.ExternalServices;
 using OrderService.Infrastructure.Idempotency;
 using OrderService.Infrastructure.Repositories;

@@ -52,6 +53,9 @@ public static class DependencyInjection
        // EN: Register idempotency services / VI: Đăng ký idempotency services
        services.AddScoped<IRequestManager, RequestManager>();

+        // EN: Register external service clients / VI: Đăng ký external service clients
+        services.AddScoped<IWalletServiceClient, WalletServiceClient>();
+
        return services;
    }
 }
--- a/services/order-service-net/src/OrderService.Infrastructure/EntityConfigurations/OrderEntityTypeConfiguration.cs
+++ b/services/order-service-net/src/OrderService.Infrastructure/EntityConfigurations/OrderEntityTypeConfiguration.cs
@@ -65,6 +65,22 @@ public class OrderEntityTypeConfiguration : IEntityTypeConfiguration<Order>
            .HasColumnName("discount_reference")
            .HasMaxLength(255);

+        builder.Property<string?>("_paymentMethod")
+            .HasColumnName("payment_method")
+            .HasMaxLength(50);
+
+        builder.Property<string?>("_transactionId")
+            .HasColumnName("transaction_id")
+            .HasMaxLength(255);
+
+        builder.Property<decimal?>("_amountTendered")
+            .HasColumnName("amount_tendered")
+            .HasColumnType("decimal(18,2)");
+
+        builder.Property<decimal?>("_changeAmount")
+            .HasColumnName("change_amount")
+            .HasColumnType("decimal(18,2)");
+
        // EN: OrderItems collection
        // VI: Collection OrderItems
        builder.OwnsMany(o => o.Items, orderItems =>
@@ -147,6 +163,10 @@ public class OrderEntityTypeConfiguration : IEntityTypeConfiguration<Order>
        builder.Ignore(o => o.DiscountAmount);
        builder.Ignore(o => o.DiscountType);
        builder.Ignore(o => o.DiscountReference);
+        builder.Ignore(o => o.PaymentMethod);
+        builder.Ignore(o => o.TransactionId);
+        builder.Ignore(o => o.AmountTendered);
+        builder.Ignore(o => o.ChangeAmount);
        builder.Ignore(o => o.CreatedAt);
        builder.Ignore(o => o.UpdatedAt);
    }
--- a/services/order-service-net/src/OrderService.Infrastructure/EntityConfigurations/OrderStatusEntityTypeConfiguration.cs
+++ b/services/order-service-net/src/OrderService.Infrastructure/EntityConfigurations/OrderStatusEntityTypeConfiguration.cs
@@ -36,7 +36,8 @@ public class OrderStatusEntityTypeConfiguration : IEntityTypeConfiguration<Order
            OrderStatus.Paid,
            OrderStatus.Processing,
            OrderStatus.Completed,
-            OrderStatus.Cancelled
+            OrderStatus.Cancelled,
+            OrderStatus.PaymentPending
        );
    }
 }
--- a/services/order-service-net/src/OrderService.Infrastructure/ExternalServices/IWalletServiceClient.cs
+++ b/services/order-service-net/src/OrderService.Infrastructure/ExternalServices/IWalletServiceClient.cs
@@ -0,0 +1,40 @@
+// EN: Interface for wallet-service client — abstracts payment gateway interaction.
+// VI: Interface cho wallet-service client — trừu tượng hóa tương tác cổng thanh toán.
+
+namespace OrderService.Infrastructure.ExternalServices;
+
+/// <summary>
+/// EN: Client interface for communicating with wallet-service for payment processing.
+/// VI: Interface client để giao tiếp với wallet-service cho xử lý thanh toán.
+/// </summary>
+public interface IWalletServiceClient
+{
+    /// <summary>
+    /// EN: Create a payment request via wallet-service. Returns payment URL for online gateways.
+    /// VI: Tạo yêu cầu thanh toán qua wallet-service. Trả về URL thanh toán cho cổng trực tuyến.
+    /// </summary>
+    /// <param name="orderId">EN: Order ID / VI: Mã đơn hàng</param>
+    /// <param name="amount">EN: Payment amount / VI: Số tiền thanh toán</param>
+    /// <param name="gateway">EN: Payment gateway (vnpay, momo) / VI: Cổng thanh toán (vnpay, momo)</param>
+    /// <param name="returnUrl">EN: URL to redirect after payment / VI: URL redirect sau thanh toán</param>
+    /// <param name="ipAddress">EN: Client IP address / VI: Địa chỉ IP client</param>
+    /// <param name="cancellationToken">EN: Cancellation token / VI: Token hủy</param>
+    /// <returns>EN: Payment creation response with URL and transaction ID / VI: Response tạo thanh toán với URL và mã giao dịch</returns>
+    Task<CreatePaymentResponse?> CreatePaymentAsync(
+        Guid orderId,
+        decimal amount,
+        string gateway,
+        string returnUrl,
+        string ipAddress,
+        CancellationToken cancellationToken = default);
+}
+
+/// <summary>
+/// EN: Response from wallet-service payment creation.
+/// VI: Response từ wallet-service khi tạo thanh toán.
+/// </summary>
+public record CreatePaymentResponse(
+    string TransactionId,
+    string PaymentUrl,
+    string Status
+);
--- a/services/order-service-net/src/OrderService.Infrastructure/ExternalServices/WalletServiceClient.cs
+++ b/services/order-service-net/src/OrderService.Infrastructure/ExternalServices/WalletServiceClient.cs
@@ -0,0 +1,78 @@
+// EN: HttpClient-based implementation of IWalletServiceClient.
+// VI: Implementation dựa trên HttpClient của IWalletServiceClient.
+
+using System.Net.Http.Json;
+using System.Text.Json;
+using Microsoft.Extensions.Logging;
+
+namespace OrderService.Infrastructure.ExternalServices;
+
+/// <summary>
+/// EN: Wallet-service client — calls wallet-service REST API for payment creation.
+/// VI: Wallet-service client — gọi wallet-service REST API để tạo thanh toán.
+/// </summary>
+public class WalletServiceClient : IWalletServiceClient
+{
+    private readonly HttpClient _httpClient;
+    private readonly ILogger<WalletServiceClient> _logger;
+
+    private static readonly JsonSerializerOptions _jsonOptions = new()
+    {
+        PropertyNameCaseInsensitive = true
+    };
+
+    public WalletServiceClient(
+        HttpClient httpClient,
+        ILogger<WalletServiceClient> logger)
+    {
+        _httpClient = httpClient ?? throw new ArgumentNullException(nameof(httpClient));
+        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
+    }
+
+    /// <inheritdoc />
+    public async Task<CreatePaymentResponse?> CreatePaymentAsync(
+        Guid orderId,
+        decimal amount,
+        string gateway,
+        string returnUrl,
+        string ipAddress,
+        CancellationToken cancellationToken = default)
+    {
+        _logger.LogInformation(
+            "EN: Creating payment via wallet-service: orderId={OrderId}, amount={Amount}, gateway={Gateway} / VI: Tạo thanh toán qua wallet-service: orderId={OrderId}, amount={Amount}, gateway={Gateway}",
+            orderId, amount, gateway);
+
+        var request = new
+        {
+            orderId,
+            amount,
+            gateway,
+            returnUrl,
+            ipAddress,
+            description = $"Payment for order {orderId}"
+        };
+
+        var response = await _httpClient.PostAsJsonAsync(
+            "/api/v1/payments/create",
+            request,
+            cancellationToken);
+
+        if (!response.IsSuccessStatusCode)
+        {
+            var errorContent = await response.Content.ReadAsStringAsync(cancellationToken);
+            _logger.LogError(
+                "EN: Wallet-service payment creation failed: {StatusCode} - {Error} / VI: Tạo thanh toán wallet-service thất bại: {StatusCode} - {Error}",
+                response.StatusCode, errorContent);
+            return null;
+        }
+
+        var result = await response.Content.ReadFromJsonAsync<CreatePaymentResponse>(
+            _jsonOptions, cancellationToken);
+
+        _logger.LogInformation(
+            "EN: Payment created successfully: txnId={TxnId} / VI: Tạo thanh toán thành công: txnId={TxnId}",
+            result?.TransactionId);
+
+        return result;
+    }
+}
--- a/services/order-service-net/tests/OrderService.UnitTests/Domain/OrderAggregateTests.cs
+++ b/services/order-service-net/tests/OrderService.UnitTests/Domain/OrderAggregateTests.cs
@@ -68,7 +68,7 @@ public class OrderAggregateTests

        // Act
        order.MarkAsValidated();
-        order.MarkAsPaid();
+        order.MarkAsPaid("cash", "TXN-TEST-001");
        order.MarkAsProcessing();
        order.MarkAsCompleted();

@@ -83,7 +83,7 @@ public class OrderAggregateTests
        var order = new Order(Guid.NewGuid());
        order.AddItem(new OrderItem(Guid.NewGuid(), "Laptop", "Physical", 1, 25_000_000m));
        order.MarkAsValidated();
-        order.MarkAsPaid();
+        order.MarkAsPaid("cash", "TXN-TEST-001");
        order.MarkAsProcessing();
        order.MarkAsCompleted();

--- a/services/wallet-service-net/src/WalletService.API/Application/Commands/Payments/CreatePaymentCommand.cs
+++ b/services/wallet-service-net/src/WalletService.API/Application/Commands/Payments/CreatePaymentCommand.cs
@@ -0,0 +1,31 @@
+namespace WalletService.API.Application.Commands.Payments;
+
+using MediatR;
+
+/// <summary>
+/// EN: Command to create a payment through a payment gateway.
+/// VI: Command de tao thanh toan qua cong thanh toan.
+/// </summary>
+public record CreatePaymentCommand(
+    Guid OrderId,
+    decimal Amount,
+    string Currency,
+    string GatewayName,
+    string ReturnUrl,
+    string IpAddress
+) : IRequest<CreatePaymentResult>;
+
+/// <summary>
+/// EN: Result of creating a payment.
+/// VI: Ket qua cua viec tao thanh toan.
+/// </summary>
+public record CreatePaymentResult(
+    Guid PaymentId,
+    Guid OrderId,
+    decimal Amount,
+    string Currency,
+    string GatewayName,
+    string Status,
+    string? PaymentUrl,
+    DateTime CreatedAt
+);
--- a/services/wallet-service-net/src/WalletService.API/Application/Commands/Payments/CreatePaymentCommandHandler.cs
+++ b/services/wallet-service-net/src/WalletService.API/Application/Commands/Payments/CreatePaymentCommandHandler.cs
@@ -0,0 +1,95 @@
+namespace WalletService.API.Application.Commands.Payments;
+
+using MediatR;
+using WalletService.Domain.AggregatesModel.PaymentAggregate;
+using WalletService.Domain.Exceptions;
+
+/// <summary>
+/// EN: Handler for CreatePaymentCommand. Creates a payment entity and initiates payment via gateway.
+/// VI: Handler cho CreatePaymentCommand. Tao entity thanh toan va bat dau thanh toan qua cong thanh toan.
+/// </summary>
+public class CreatePaymentCommandHandler : IRequestHandler<CreatePaymentCommand, CreatePaymentResult>
+{
+    private readonly IPaymentRepository _paymentRepository;
+    private readonly IEnumerable<IPaymentGateway> _paymentGateways;
+    private readonly ILogger<CreatePaymentCommandHandler> _logger;
+
+    public CreatePaymentCommandHandler(
+        IPaymentRepository paymentRepository,
+        IEnumerable<IPaymentGateway> paymentGateways,
+        ILogger<CreatePaymentCommandHandler> logger)
+    {
+        _paymentRepository = paymentRepository;
+        _paymentGateways = paymentGateways;
+        _logger = logger;
+    }
+
+    public async Task<CreatePaymentResult> Handle(
+        CreatePaymentCommand request,
+        CancellationToken cancellationToken)
+    {
+        _logger.LogInformation(
+            "EN: Creating payment for order {OrderId}, gateway {GatewayName} / " +
+            "VI: Tao thanh toan cho don hang {OrderId}, cong thanh toan {GatewayName}",
+            request.OrderId, request.GatewayName);
+
+        // EN: Find the requested payment gateway
+        // VI: Tim cong thanh toan duoc yeu cau
+        var gateway = _paymentGateways.FirstOrDefault(
+            g => g.GatewayName.Equals(request.GatewayName, StringComparison.OrdinalIgnoreCase))
+            ?? throw new WalletDomainException(
+                $"Payment gateway '{request.GatewayName}' is not supported / " +
+                $"Cong thanh toan '{request.GatewayName}' khong duoc ho tro");
+
+        // EN: Create payment entity
+        // VI: Tao entity thanh toan
+        var payment = new Payment(
+            request.OrderId,
+            request.Amount,
+            request.Currency,
+            gateway.GatewayName);
+
+        // EN: Call gateway to create payment
+        // VI: Goi cong thanh toan de tao thanh toan
+        var paymentRequest = new PaymentRequest(
+            request.OrderId,
+            request.Amount,
+            request.Currency,
+            $"Payment for order {request.OrderId}",
+            request.ReturnUrl,
+            request.IpAddress);
+
+        var gatewayResult = await gateway.CreatePaymentAsync(paymentRequest, cancellationToken);
+
+        if (gatewayResult.Success)
+        {
+            // EN: Mark as processing with payment URL
+            // VI: Danh dau dang xu ly voi URL thanh toan
+            payment.MarkAsProcessing(gatewayResult.PaymentUrl, gatewayResult.TransactionId);
+        }
+        else
+        {
+            // EN: Mark as failed
+            // VI: Danh dau that bai
+            payment.Fail(gatewayResult.ErrorCode, gatewayResult.ErrorMessage);
+        }
+
+        _paymentRepository.Add(payment);
+        await _paymentRepository.UnitOfWork.SaveEntitiesAsync(cancellationToken);
+
+        _logger.LogInformation(
+            "EN: Payment {PaymentId} created for order {OrderId}, status: {Status} / " +
+            "VI: Thanh toan {PaymentId} da tao cho don hang {OrderId}, trang thai: {Status}",
+            payment.Id, request.OrderId, payment.Status.Name);
+
+        return new CreatePaymentResult(
+            payment.Id,
+            payment.OrderId,
+            payment.Amount,
+            payment.Currency,
+            payment.GatewayName,
+            payment.Status.Name,
+            payment.PaymentUrl,
+            payment.CreatedAt);
+    }
+}
--- a/services/wallet-service-net/src/WalletService.API/Application/Commands/Payments/ProcessPaymentCallbackCommand.cs
+++ b/services/wallet-service-net/src/WalletService.API/Application/Commands/Payments/ProcessPaymentCallbackCommand.cs
@@ -0,0 +1,24 @@
+namespace WalletService.API.Application.Commands.Payments;
+
+using MediatR;
+
+/// <summary>
+/// EN: Command to process a payment gateway callback (IPN).
+/// VI: Command de xu ly callback (IPN) tu cong thanh toan.
+/// </summary>
+public record ProcessPaymentCallbackCommand(
+    string GatewayName,
+    IDictionary<string, string> Parameters
+) : IRequest<ProcessPaymentCallbackResult>;
+
+/// <summary>
+/// EN: Result of processing a payment callback.
+/// VI: Ket qua xu ly callback thanh toan.
+/// </summary>
+public record ProcessPaymentCallbackResult(
+    bool Success,
+    Guid? PaymentId,
+    Guid? OrderId,
+    string Status,
+    string? ErrorMessage
+);
--- a/services/wallet-service-net/src/WalletService.API/Application/Commands/Payments/ProcessPaymentCallbackCommandHandler.cs
+++ b/services/wallet-service-net/src/WalletService.API/Application/Commands/Payments/ProcessPaymentCallbackCommandHandler.cs
@@ -0,0 +1,134 @@
+namespace WalletService.API.Application.Commands.Payments;
+
+using MediatR;
+using WalletService.Domain.AggregatesModel.PaymentAggregate;
+using WalletService.Domain.Exceptions;
+
+/// <summary>
+/// EN: Handler for ProcessPaymentCallbackCommand. Validates gateway callback and updates payment status.
+/// VI: Handler cho ProcessPaymentCallbackCommand. Xac thuc callback cong thanh toan va cap nhat trang thai.
+/// </summary>
+public class ProcessPaymentCallbackCommandHandler
+    : IRequestHandler<ProcessPaymentCallbackCommand, ProcessPaymentCallbackResult>
+{
+    private readonly IPaymentRepository _paymentRepository;
+    private readonly IEnumerable<IPaymentGateway> _paymentGateways;
+    private readonly ILogger<ProcessPaymentCallbackCommandHandler> _logger;
+
+    public ProcessPaymentCallbackCommandHandler(
+        IPaymentRepository paymentRepository,
+        IEnumerable<IPaymentGateway> paymentGateways,
+        ILogger<ProcessPaymentCallbackCommandHandler> logger)
+    {
+        _paymentRepository = paymentRepository;
+        _paymentGateways = paymentGateways;
+        _logger = logger;
+    }
+
+    public async Task<ProcessPaymentCallbackResult> Handle(
+        ProcessPaymentCallbackCommand request,
+        CancellationToken cancellationToken)
+    {
+        _logger.LogInformation(
+            "EN: Processing payment callback from gateway {GatewayName} / " +
+            "VI: Xu ly callback thanh toan tu cong thanh toan {GatewayName}",
+            request.GatewayName);
+
+        // EN: Find the payment gateway
+        // VI: Tim cong thanh toan
+        var gateway = _paymentGateways.FirstOrDefault(
+            g => g.GatewayName.Equals(request.GatewayName, StringComparison.OrdinalIgnoreCase))
+            ?? throw new WalletDomainException(
+                $"Payment gateway '{request.GatewayName}' is not supported / " +
+                $"Cong thanh toan '{request.GatewayName}' khong duoc ho tro");
+
+        // EN: Validate callback hash
+        // VI: Xac thuc hash callback
+        request.Parameters.TryGetValue("vnp_SecureHash", out var secureHash);
+        if (!gateway.ValidateCallback(request.Parameters, secureHash ?? string.Empty))
+        {
+            _logger.LogWarning(
+                "EN: Invalid callback signature from {GatewayName} / " +
+                "VI: Chu ky callback khong hop le tu {GatewayName}",
+                request.GatewayName);
+
+            return new ProcessPaymentCallbackResult(
+                Success: false,
+                PaymentId: null,
+                OrderId: null,
+                Status: "InvalidSignature",
+                ErrorMessage: "Invalid callback signature / Chu ky callback khong hop le");
+        }
+
+        // EN: Find the payment by transaction reference
+        // VI: Tim thanh toan theo tham chieu giao dich
+        request.Parameters.TryGetValue("vnp_TxnRef", out var txnRef);
+        if (!Guid.TryParse(txnRef, out var orderId))
+        {
+            return new ProcessPaymentCallbackResult(
+                Success: false,
+                PaymentId: null,
+                OrderId: null,
+                Status: "InvalidReference",
+                ErrorMessage: "Invalid transaction reference / Tham chieu giao dich khong hop le");
+        }
+
+        var payment = await _paymentRepository.GetByOrderIdAsync(orderId);
+        if (payment == null)
+        {
+            _logger.LogWarning(
+                "EN: Payment not found for order {OrderId} / " +
+                "VI: Khong tim thay thanh toan cho don hang {OrderId}",
+                orderId);
+
+            return new ProcessPaymentCallbackResult(
+                Success: false,
+                PaymentId: null,
+                OrderId: orderId,
+                Status: "NotFound",
+                ErrorMessage: "Payment not found / Khong tim thay thanh toan");
+        }
+
+        // EN: Process the callback based on response code
+        // VI: Xu ly callback dua tren ma phan hoi
+        request.Parameters.TryGetValue("vnp_ResponseCode", out var responseCode);
+        responseCode ??= "99";
+        request.Parameters.TryGetValue("vnp_TransactionNo", out var transactionNo);
+        transactionNo ??= string.Empty;
+
+        if (responseCode == "00")
+        {
+            // EN: Payment successful
+            // VI: Thanh toan thanh cong
+            payment.Complete(transactionNo);
+
+            _logger.LogInformation(
+                "EN: Payment {PaymentId} completed for order {OrderId} / " +
+                "VI: Thanh toan {PaymentId} hoan thanh cho don hang {OrderId}",
+                payment.Id, orderId);
+        }
+        else
+        {
+            // EN: Payment failed
+            // VI: Thanh toan that bai
+            request.Parameters.TryGetValue("vnp_OrderInfo", out var errorMessage);
+            errorMessage ??= "Payment failed";
+            payment.Fail(responseCode, errorMessage);
+
+            _logger.LogWarning(
+                "EN: Payment {PaymentId} failed for order {OrderId}, code: {ErrorCode} / " +
+                "VI: Thanh toan {PaymentId} that bai cho don hang {OrderId}, ma: {ErrorCode}",
+                payment.Id, orderId, responseCode);
+        }
+
+        _paymentRepository.Update(payment);
+        await _paymentRepository.UnitOfWork.SaveEntitiesAsync(cancellationToken);
+
+        return new ProcessPaymentCallbackResult(
+            Success: responseCode == "00",
+            PaymentId: payment.Id,
+            OrderId: orderId,
+            Status: payment.Status.Name,
+            ErrorMessage: responseCode == "00" ? null : $"VN Pay response code: {responseCode}");
+    }
+}
--- a/services/wallet-service-net/src/WalletService.API/Application/Queries/Payments/GetPaymentQuery.cs
+++ b/services/wallet-service-net/src/WalletService.API/Application/Queries/Payments/GetPaymentQuery.cs
@@ -0,0 +1,34 @@
+namespace WalletService.API.Application.Queries.Payments;
+
+using MediatR;
+
+/// <summary>
+/// EN: Query to get a payment by order ID.
+/// VI: Query de lay thanh toan theo ma don hang.
+/// </summary>
+public record GetPaymentByOrderIdQuery(Guid OrderId) : IRequest<PaymentDto?>;
+
+/// <summary>
+/// EN: Query to get a payment by gateway transaction ID.
+/// VI: Query de lay thanh toan theo ma giao dich cong thanh toan.
+/// </summary>
+public record GetPaymentByTransactionIdQuery(string TransactionId) : IRequest<PaymentDto?>;
+
+/// <summary>
+/// EN: DTO representing a payment transaction.
+/// VI: DTO dai dien cho giao dich thanh toan.
+/// </summary>
+public record PaymentDto(
+    Guid PaymentId,
+    Guid OrderId,
+    decimal Amount,
+    string Currency,
+    string GatewayName,
+    string? TransactionId,
+    string? PaymentUrl,
+    string Status,
+    string? ErrorCode,
+    string? ErrorMessage,
+    DateTime CreatedAt,
+    DateTime? CompletedAt
+);
--- a/services/wallet-service-net/src/WalletService.API/Application/Queries/Payments/GetPaymentQueryHandler.cs
+++ b/services/wallet-service-net/src/WalletService.API/Application/Queries/Payments/GetPaymentQueryHandler.cs
@@ -0,0 +1,99 @@
+namespace WalletService.API.Application.Queries.Payments;
+
+using MediatR;
+using WalletService.Domain.AggregatesModel.PaymentAggregate;
+
+/// <summary>
+/// EN: Handler for GetPaymentByOrderIdQuery.
+/// VI: Handler cho GetPaymentByOrderIdQuery.
+/// </summary>
+public class GetPaymentByOrderIdQueryHandler : IRequestHandler<GetPaymentByOrderIdQuery, PaymentDto?>
+{
+    private readonly IPaymentRepository _paymentRepository;
+    private readonly ILogger<GetPaymentByOrderIdQueryHandler> _logger;
+
+    public GetPaymentByOrderIdQueryHandler(
+        IPaymentRepository paymentRepository,
+        ILogger<GetPaymentByOrderIdQueryHandler> logger)
+    {
+        _paymentRepository = paymentRepository;
+        _logger = logger;
+    }
+
+    public async Task<PaymentDto?> Handle(
+        GetPaymentByOrderIdQuery request,
+        CancellationToken cancellationToken)
+    {
+        _logger.LogInformation(
+            "EN: Getting payment for order {OrderId} / " +
+            "VI: Lay thanh toan cho don hang {OrderId}",
+            request.OrderId);
+
+        var payment = await _paymentRepository.GetByOrderIdAsync(request.OrderId);
+
+        return payment == null ? null : MapToDto(payment);
+    }
+
+    private static PaymentDto MapToDto(Payment payment)
+    {
+        return new PaymentDto(
+            payment.Id,
+            payment.OrderId,
+            payment.Amount,
+            payment.Currency,
+            payment.GatewayName,
+            payment.TransactionId,
+            payment.PaymentUrl,
+            payment.Status.Name,
+            payment.ErrorCode,
+            payment.ErrorMessage,
+            payment.CreatedAt,
+            payment.CompletedAt);
+    }
+}
+
+/// <summary>
+/// EN: Handler for GetPaymentByTransactionIdQuery.
+/// VI: Handler cho GetPaymentByTransactionIdQuery.
+/// </summary>
+public class GetPaymentByTransactionIdQueryHandler : IRequestHandler<GetPaymentByTransactionIdQuery, PaymentDto?>
+{
+    private readonly IPaymentRepository _paymentRepository;
+    private readonly ILogger<GetPaymentByTransactionIdQueryHandler> _logger;
+
+    public GetPaymentByTransactionIdQueryHandler(
+        IPaymentRepository paymentRepository,
+        ILogger<GetPaymentByTransactionIdQueryHandler> logger)
+    {
+        _paymentRepository = paymentRepository;
+        _logger = logger;
+    }
+
+    public async Task<PaymentDto?> Handle(
+        GetPaymentByTransactionIdQuery request,
+        CancellationToken cancellationToken)
+    {
+        _logger.LogInformation(
+            "EN: Getting payment by transaction ID {TransactionId} / " +
+            "VI: Lay thanh toan theo ma giao dich {TransactionId}",
+            request.TransactionId);
+
+        var payment = await _paymentRepository.GetByTransactionIdAsync(request.TransactionId);
+
+        if (payment == null) return null;
+
+        return new PaymentDto(
+            payment.Id,
+            payment.OrderId,
+            payment.Amount,
+            payment.Currency,
+            payment.GatewayName,
+            payment.TransactionId,
+            payment.PaymentUrl,
+            payment.Status.Name,
+            payment.ErrorCode,
+            payment.ErrorMessage,
+            payment.CreatedAt,
+            payment.CompletedAt);
+    }
+}
--- a/services/wallet-service-net/src/WalletService.API/Application/Validations/CreatePaymentCommandValidator.cs
+++ b/services/wallet-service-net/src/WalletService.API/Application/Validations/CreatePaymentCommandValidator.cs
@@ -0,0 +1,64 @@
+namespace WalletService.API.Application.Validations;
+
+using FluentValidation;
+using WalletService.API.Application.Commands.Payments;
+
+/// <summary>
+/// EN: Validator for CreatePaymentCommand.
+/// VI: Validator cho CreatePaymentCommand.
+/// </summary>
+public class CreatePaymentCommandValidator : AbstractValidator<CreatePaymentCommand>
+{
+    public CreatePaymentCommandValidator()
+    {
+        RuleFor(x => x.OrderId)
+            .NotEmpty()
+            .WithMessage("Order ID is required / Ma don hang la bat buoc");
+
+        RuleFor(x => x.Amount)
+            .GreaterThan(0)
+            .WithMessage("Amount must be greater than zero / So tien phai lon hon 0");
+
+        RuleFor(x => x.Currency)
+            .NotEmpty()
+            .WithMessage("Currency is required / Tien te la bat buoc")
+            .MaximumLength(10)
+            .WithMessage("Currency code must not exceed 10 characters / Ma tien te khong vuot qua 10 ky tu");
+
+        RuleFor(x => x.GatewayName)
+            .NotEmpty()
+            .WithMessage("Gateway name is required / Ten cong thanh toan la bat buoc")
+            .MaximumLength(50)
+            .WithMessage("Gateway name must not exceed 50 characters / Ten cong thanh toan khong vuot qua 50 ky tu");
+
+        RuleFor(x => x.ReturnUrl)
+            .NotEmpty()
+            .WithMessage("Return URL is required / URL tra ve la bat buoc")
+            .Must(url => Uri.TryCreate(url, UriKind.Absolute, out _))
+            .WithMessage("Return URL must be a valid URL / URL tra ve phai hop le");
+
+        RuleFor(x => x.IpAddress)
+            .NotEmpty()
+            .WithMessage("IP address is required / Dia chi IP la bat buoc");
+    }
+}
+
+/// <summary>
+/// EN: Validator for ProcessPaymentCallbackCommand.
+/// VI: Validator cho ProcessPaymentCallbackCommand.
+/// </summary>
+public class ProcessPaymentCallbackCommandValidator : AbstractValidator<ProcessPaymentCallbackCommand>
+{
+    public ProcessPaymentCallbackCommandValidator()
+    {
+        RuleFor(x => x.GatewayName)
+            .NotEmpty()
+            .WithMessage("Gateway name is required / Ten cong thanh toan la bat buoc");
+
+        RuleFor(x => x.Parameters)
+            .NotNull()
+            .WithMessage("Callback parameters are required / Cac tham so callback la bat buoc")
+            .Must(p => p.Count > 0)
+            .WithMessage("Callback parameters cannot be empty / Cac tham so callback khong duoc trong");
+    }
+}
--- a/services/wallet-service-net/src/WalletService.API/Controllers/PaymentsController.cs
+++ b/services/wallet-service-net/src/WalletService.API/Controllers/PaymentsController.cs
@@ -0,0 +1,161 @@
+namespace WalletService.API.Controllers;
+
+using MediatR;
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Mvc;
+using Swashbuckle.AspNetCore.Annotations;
+using WalletService.API.Application.Commands.Payments;
+using WalletService.API.Application.Queries.Payments;
+
+/// <summary>
+/// EN: Controller for payment gateway operations.
+/// VI: Controller cho cac thao tac cong thanh toan.
+/// </summary>
+[ApiController]
+[Route("api/v1/[controller]")]
+[SwaggerTag("Payment gateway endpoints / Cac endpoint cong thanh toan")]
+public class PaymentsController : ControllerBase
+{
+    private readonly IMediator _mediator;
+    private readonly ILogger<PaymentsController> _logger;
+
+    public PaymentsController(IMediator mediator, ILogger<PaymentsController> logger)
+    {
+        _mediator = mediator;
+        _logger = logger;
+    }
+
+    /// <summary>
+    /// EN: Create a payment through a payment gateway.
+    /// VI: Tao thanh toan qua cong thanh toan.
+    /// </summary>
+    [HttpPost("create")]
+    [Authorize]
+    [SwaggerOperation(Summary = "Create payment", Description = "Create a payment via payment gateway (VNPay, etc.)")]
+    [SwaggerResponse(201, "Payment created", typeof(ApiResponse<CreatePaymentResult>))]
+    [SwaggerResponse(400, "Invalid request")]
+    public async Task<IActionResult> CreatePayment(
+        [FromBody] CreatePaymentRequest request,
+        CancellationToken cancellationToken)
+    {
+        var ipAddress = HttpContext.Connection.RemoteIpAddress?.ToString() ?? "127.0.0.1";
+
+        var command = new CreatePaymentCommand(
+            request.OrderId,
+            request.Amount,
+            request.Currency ?? "VND",
+            request.GatewayName ?? "VNPAY",
+            request.ReturnUrl,
+            ipAddress);
+
+        var result = await _mediator.Send(command, cancellationToken);
+
+        return CreatedAtAction(
+            nameof(GetPaymentByOrderId),
+            new { orderId = result.OrderId },
+            new ApiResponse<CreatePaymentResult>(true, "Payment created / Thanh toan da duoc tao", result));
+    }
+
+    /// <summary>
+    /// EN: Get payment by order ID.
+    /// VI: Lay thanh toan theo ma don hang.
+    /// </summary>
+    [HttpGet("{orderId:guid}")]
+    [Authorize]
+    [SwaggerOperation(Summary = "Get payment", Description = "Get payment information by order ID")]
+    [SwaggerResponse(200, "Success", typeof(ApiResponse<PaymentDto>))]
+    [SwaggerResponse(404, "Payment not found")]
+    public async Task<IActionResult> GetPaymentByOrderId(
+        Guid orderId,
+        CancellationToken cancellationToken)
+    {
+        var result = await _mediator.Send(new GetPaymentByOrderIdQuery(orderId), cancellationToken);
+
+        if (result == null)
+            return NotFound(new ApiResponse<object>(false, "Payment not found / Khong tim thay thanh toan"));
+
+        return Ok(new ApiResponse<PaymentDto>(true, "Success", result));
+    }
+
+    /// <summary>
+    /// EN: VN Pay IPN callback endpoint (called by VN Pay server).
+    /// VI: Endpoint IPN callback VN Pay (duoc goi boi server VN Pay).
+    /// </summary>
+    /// <remarks>
+    /// EN: This endpoint does NOT require authentication as it is called by VN Pay servers.
+    /// VI: Endpoint nay KHONG yeu cau xac thuc vi no duoc goi boi server VN Pay.
+    /// </remarks>
+    [HttpGet("vnpay/callback")]
+    [AllowAnonymous]
+    [SwaggerOperation(Summary = "VN Pay IPN callback", Description = "VN Pay server calls this endpoint to notify payment status")]
+    [SwaggerResponse(200, "Callback processed")]
+    public async Task<IActionResult> VnPayCallback(CancellationToken cancellationToken)
+    {
+        _logger.LogInformation(
+            "EN: Received VN Pay IPN callback / " +
+            "VI: Nhan IPN callback tu VN Pay");
+
+        // EN: Collect all query parameters
+        // VI: Thu thap tat ca cac tham so query
+        var parameters = HttpContext.Request.Query
+            .ToDictionary(q => q.Key, q => q.Value.ToString());
+
+        var command = new ProcessPaymentCallbackCommand("VNPAY", parameters);
+        var result = await _mediator.Send(command, cancellationToken);
+
+        // EN: VN Pay expects specific response format
+        // VI: VN Pay yeu cau format phan hoi cu the
+        if (result.Success)
+        {
+            return Ok(new { RspCode = "00", Message = "Confirm Success" });
+        }
+
+        return Ok(new { RspCode = "99", Message = result.ErrorMessage ?? "Unknown error" });
+    }
+
+    /// <summary>
+    /// EN: VN Pay return URL handler (customer is redirected here after payment).
+    /// VI: Handler URL tra ve VN Pay (khach hang duoc chuyen huong den day sau thanh toan).
+    /// </summary>
+    [HttpGet("vnpay/return")]
+    [AllowAnonymous]
+    [SwaggerOperation(Summary = "VN Pay return", Description = "Customer is redirected here after VN Pay payment")]
+    [SwaggerResponse(200, "Payment result")]
+    public async Task<IActionResult> VnPayReturn(CancellationToken cancellationToken)
+    {
+        _logger.LogInformation(
+            "EN: Customer returned from VN Pay / " +
+            "VI: Khach hang quay ve tu VN Pay");
+
+        // EN: Collect all query parameters
+        // VI: Thu thap tat ca cac tham so query
+        var parameters = HttpContext.Request.Query
+            .ToDictionary(q => q.Key, q => q.Value.ToString());
+
+        var command = new ProcessPaymentCallbackCommand("VNPAY", parameters);
+        var result = await _mediator.Send(command, cancellationToken);
+
+        return Ok(new ApiResponse<ProcessPaymentCallbackResult>(
+            result.Success,
+            result.Success
+                ? "Payment successful / Thanh toan thanh cong"
+                : "Payment failed / Thanh toan that bai",
+            result));
+    }
+}
+
+#region Request DTOs
+
+/// <summary>
+/// EN: Request DTO for creating a payment.
+/// VI: DTO yeu cau de tao thanh toan.
+/// </summary>
+public record CreatePaymentRequest(
+    Guid OrderId,
+    decimal Amount,
+    string? Currency,
+    string? GatewayName,
+    string ReturnUrl
+);
+
+#endregion
--- a/services/wallet-service-net/src/WalletService.API/appsettings.Development.json
+++ b/services/wallet-service-net/src/WalletService.API/appsettings.Development.json
@@ -15,5 +15,12 @@
                "System": "Information"
            }
        }
+    },
+    "VnPay": {
+        "TmnCode": "GOODGO01",
+        "HashSecret": "GOODGOSECRETKEYFORSANDBOX2026",
+        "PaymentUrl": "https://sandbox.vnpayment.vn/paymentv2/vpcpay.html",
+        "ReturnUrl": "http://localhost:3001/payment/return",
+        "ApiUrl": "https://sandbox.vnpayment.vn/merchant_webapi/api/transaction"
    }
 }
--- a/services/wallet-service-net/src/WalletService.Domain/AggregatesModel/PaymentAggregate/IPaymentGateway.cs
+++ b/services/wallet-service-net/src/WalletService.Domain/AggregatesModel/PaymentAggregate/IPaymentGateway.cs
@@ -0,0 +1,55 @@
+namespace WalletService.Domain.AggregatesModel.PaymentAggregate;
+
+/// <summary>
+/// EN: Abstraction for payment gateway integrations.
+/// VI: Abstraction cho tich hop cong thanh toan.
+/// </summary>
+/// <remarks>
+/// EN: Each payment gateway (VNPay, MoMo, ZaloPay, etc.) implements this interface.
+/// VI: Moi cong thanh toan (VNPay, MoMo, ZaloPay, v.v.) implement interface nay.
+/// </remarks>
+public interface IPaymentGateway
+{
+    /// <summary>
+    /// EN: The name of this payment gateway.
+    /// VI: Ten cua cong thanh toan nay.
+    /// </summary>
+    string GatewayName { get; }
+
+    /// <summary>
+    /// EN: Create a payment request and get the payment URL.
+    /// VI: Tao yeu cau thanh toan va lay URL thanh toan.
+    /// </summary>
+    /// <param name="request">EN: Payment request details / VI: Chi tiet yeu cau thanh toan</param>
+    /// <param name="cancellationToken">EN: Cancellation token / VI: Token huy</param>
+    /// <returns>EN: Payment result with payment URL / VI: Ket qua thanh toan voi URL thanh toan</returns>
+    Task<PaymentResult> CreatePaymentAsync(PaymentRequest request, CancellationToken cancellationToken);
+
+    /// <summary>
+    /// EN: Query the status of an existing payment transaction.
+    /// VI: Truy van trang thai cua giao dich thanh toan hien co.
+    /// </summary>
+    /// <param name="transactionId">EN: Transaction identifier / VI: Ma giao dich</param>
+    /// <param name="cancellationToken">EN: Cancellation token / VI: Token huy</param>
+    /// <returns>EN: Payment result with current status / VI: Ket qua thanh toan voi trang thai hien tai</returns>
+    Task<PaymentResult> QueryPaymentAsync(string transactionId, CancellationToken cancellationToken);
+
+    /// <summary>
+    /// EN: Request a refund for a completed payment.
+    /// VI: Yeu cau hoan tien cho giao dich da hoan thanh.
+    /// </summary>
+    /// <param name="transactionId">EN: Transaction identifier / VI: Ma giao dich</param>
+    /// <param name="amount">EN: Amount to refund / VI: So tien hoan</param>
+    /// <param name="cancellationToken">EN: Cancellation token / VI: Token huy</param>
+    /// <returns>EN: Payment result with refund status / VI: Ket qua thanh toan voi trang thai hoan tien</returns>
+    Task<PaymentResult> RefundAsync(string transactionId, decimal amount, CancellationToken cancellationToken);
+
+    /// <summary>
+    /// EN: Validate a callback/IPN from the payment gateway.
+    /// VI: Xac thuc callback/IPN tu cong thanh toan.
+    /// </summary>
+    /// <param name="parameters">EN: Callback parameters / VI: Cac tham so callback</param>
+    /// <param name="secureHash">EN: Secure hash from the gateway / VI: Hash bao mat tu cong thanh toan</param>
+    /// <returns>EN: True if the callback is valid / VI: True neu callback hop le</returns>
+    bool ValidateCallback(IDictionary<string, string> parameters, string secureHash);
+}
--- a/services/wallet-service-net/src/WalletService.Domain/AggregatesModel/PaymentAggregate/IPaymentRepository.cs
+++ b/services/wallet-service-net/src/WalletService.Domain/AggregatesModel/PaymentAggregate/IPaymentRepository.cs
@@ -0,0 +1,46 @@
+namespace WalletService.Domain.AggregatesModel.PaymentAggregate;
+
+using WalletService.Domain.SeedWork;
+
+/// <summary>
+/// EN: Repository interface for Payment aggregate.
+/// VI: Interface repository cho aggregate Payment.
+/// </summary>
+public interface IPaymentRepository : IRepository<Payment>
+{
+    /// <summary>
+    /// EN: Get payment by ID.
+    /// VI: Lay thanh toan theo ID.
+    /// </summary>
+    Task<Payment?> GetByIdAsync(Guid paymentId);
+
+    /// <summary>
+    /// EN: Get payment by order ID.
+    /// VI: Lay thanh toan theo ma don hang.
+    /// </summary>
+    Task<Payment?> GetByOrderIdAsync(Guid orderId);
+
+    /// <summary>
+    /// EN: Get payment by gateway transaction ID.
+    /// VI: Lay thanh toan theo ma giao dich cong thanh toan.
+    /// </summary>
+    Task<Payment?> GetByTransactionIdAsync(string transactionId);
+
+    /// <summary>
+    /// EN: Get payments by order ID (an order may have multiple payment attempts).
+    /// VI: Lay cac thanh toan theo ma don hang (mot don hang co the co nhieu lan thanh toan).
+    /// </summary>
+    Task<IEnumerable<Payment>> GetPaymentsByOrderIdAsync(Guid orderId);
+
+    /// <summary>
+    /// EN: Add a new payment.
+    /// VI: Them thanh toan moi.
+    /// </summary>
+    Payment Add(Payment payment);
+
+    /// <summary>
+    /// EN: Update an existing payment.
+    /// VI: Cap nhat thanh toan hien co.
+    /// </summary>
+    void Update(Payment payment);
+}
--- a/services/wallet-service-net/src/WalletService.Domain/AggregatesModel/PaymentAggregate/Payment.cs
+++ b/services/wallet-service-net/src/WalletService.Domain/AggregatesModel/PaymentAggregate/Payment.cs
@@ -0,0 +1,218 @@
+namespace WalletService.Domain.AggregatesModel.PaymentAggregate;
+
+using WalletService.Domain.Events;
+using WalletService.Domain.Exceptions;
+using WalletService.Domain.SeedWork;
+
+/// <summary>
+/// EN: Payment aggregate root representing a payment transaction through a gateway.
+/// VI: Aggregate root thanh toan dai dien cho giao dich thanh toan qua cong thanh toan.
+/// </summary>
+/// <remarks>
+/// EN: Tracks the lifecycle of a payment from creation through completion/failure/refund.
+/// VI: Theo doi vong doi cua thanh toan tu khi tao den khi hoan thanh/that bai/hoan tien.
+/// </remarks>
+public class Payment : Entity, IAggregateRoot
+{
+    private Guid _orderId;
+    private decimal _amount;
+    private string _currency;
+    private string _gatewayName;
+    private string? _transactionId;
+    private string? _paymentUrl;
+    private int _statusId;
+    private string? _errorCode;
+    private string? _errorMessage;
+    private DateTime _createdAt;
+    private DateTime? _completedAt;
+
+    /// <summary>
+    /// EN: The order identifier associated with this payment.
+    /// VI: Ma don hang lien ket voi thanh toan nay.
+    /// </summary>
+    public Guid OrderId => _orderId;
+
+    /// <summary>
+    /// EN: Payment amount.
+    /// VI: So tien thanh toan.
+    /// </summary>
+    public decimal Amount => _amount;
+
+    /// <summary>
+    /// EN: Currency code (e.g., VND, USD).
+    /// VI: Ma tien te (vd: VND, USD).
+    /// </summary>
+    public string Currency => _currency;
+
+    /// <summary>
+    /// EN: Name of the payment gateway used.
+    /// VI: Ten cong thanh toan su dung.
+    /// </summary>
+    public string GatewayName => _gatewayName;
+
+    /// <summary>
+    /// EN: Transaction ID from the payment gateway.
+    /// VI: Ma giao dich tu cong thanh toan.
+    /// </summary>
+    public string? TransactionId => _transactionId;
+
+    /// <summary>
+    /// EN: Payment URL for customer redirect.
+    /// VI: URL thanh toan de chuyen huong khach hang.
+    /// </summary>
+    public string? PaymentUrl => _paymentUrl;
+
+    /// <summary>
+    /// EN: Payment status ID for EF Core mapping.
+    /// VI: ID trang thai thanh toan cho EF Core mapping.
+    /// </summary>
+    public int StatusId => _statusId;
+
+    /// <summary>
+    /// EN: Payment status.
+    /// VI: Trang thai thanh toan.
+    /// </summary>
+    public PaymentStatus Status => PaymentStatus.FromValue<PaymentStatus>(_statusId);
+
+    /// <summary>
+    /// EN: Error code if payment failed.
+    /// VI: Ma loi neu thanh toan that bai.
+    /// </summary>
+    public string? ErrorCode => _errorCode;
+
+    /// <summary>
+    /// EN: Error message if payment failed.
+    /// VI: Thong bao loi neu thanh toan that bai.
+    /// </summary>
+    public string? ErrorMessage => _errorMessage;
+
+    /// <summary>
+    /// EN: Payment creation timestamp.
+    /// VI: Thoi diem tao thanh toan.
+    /// </summary>
+    public DateTime CreatedAt => _createdAt;
+
+    /// <summary>
+    /// EN: Payment completion timestamp.
+    /// VI: Thoi diem hoan thanh thanh toan.
+    /// </summary>
+    public DateTime? CompletedAt => _completedAt;
+
+    /// <summary>
+    /// EN: EF Core parameterless constructor.
+    /// VI: Constructor khong tham so cho EF Core.
+    /// </summary>
+    protected Payment()
+    {
+        _currency = string.Empty;
+        _gatewayName = string.Empty;
+    }
+
+    /// <summary>
+    /// EN: Create a new payment transaction.
+    /// VI: Tao giao dich thanh toan moi.
+    /// </summary>
+    /// <param name="orderId">EN: Order identifier / VI: Ma don hang</param>
+    /// <param name="amount">EN: Payment amount / VI: So tien thanh toan</param>
+    /// <param name="currency">EN: Currency code / VI: Ma tien te</param>
+    /// <param name="gatewayName">EN: Payment gateway name / VI: Ten cong thanh toan</param>
+    public Payment(Guid orderId, decimal amount, string currency, string gatewayName)
+    {
+        if (orderId == Guid.Empty)
+            throw new WalletDomainException("Order ID cannot be empty / Ma don hang khong duoc trong");
+
+        if (amount <= 0)
+            throw new WalletDomainException("Payment amount must be greater than zero / So tien thanh toan phai lon hon 0");
+
+        if (string.IsNullOrWhiteSpace(currency))
+            throw new WalletDomainException("Currency is required / Tien te la bat buoc");
+
+        if (string.IsNullOrWhiteSpace(gatewayName))
+            throw new WalletDomainException("Gateway name is required / Ten cong thanh toan la bat buoc");
+
+        Id = Guid.NewGuid();
+        _orderId = orderId;
+        _amount = amount;
+        _currency = currency.ToUpperInvariant();
+        _gatewayName = gatewayName;
+        _statusId = PaymentStatus.Pending.Id;
+        _createdAt = DateTime.UtcNow;
+
+        AddDomainEvent(new PaymentCreatedDomainEvent(Id, orderId, amount, currency, gatewayName));
+    }
+
+    /// <summary>
+    /// EN: Mark payment as processing (gateway has accepted the request).
+    /// VI: Danh dau thanh toan dang xu ly (cong thanh toan da chap nhan yeu cau).
+    /// </summary>
+    /// <param name="paymentUrl">EN: Payment URL for customer / VI: URL thanh toan cho khach hang</param>
+    /// <param name="transactionId">EN: Gateway transaction ID / VI: Ma giao dich cong thanh toan</param>
+    public void MarkAsProcessing(string? paymentUrl, string? transactionId = null)
+    {
+        if (_statusId != PaymentStatus.Pending.Id)
+            throw new WalletDomainException(
+                $"Cannot mark payment as processing from status {Status.Name} / " +
+                $"Khong the danh dau thanh toan dang xu ly tu trang thai {Status.Name}");
+
+        _statusId = PaymentStatus.Processing.Id;
+        _paymentUrl = paymentUrl;
+        _transactionId = transactionId;
+    }
+
+    /// <summary>
+    /// EN: Complete the payment successfully.
+    /// VI: Hoan thanh thanh toan thanh cong.
+    /// </summary>
+    /// <param name="transactionId">EN: Gateway transaction ID / VI: Ma giao dich cong thanh toan</param>
+    public void Complete(string transactionId)
+    {
+        if (_statusId != PaymentStatus.Pending.Id && _statusId != PaymentStatus.Processing.Id)
+            throw new WalletDomainException(
+                $"Cannot complete payment from status {Status.Name} / " +
+                $"Khong the hoan thanh thanh toan tu trang thai {Status.Name}");
+
+        if (string.IsNullOrWhiteSpace(transactionId))
+            throw new WalletDomainException("Transaction ID is required / Ma giao dich la bat buoc");
+
+        _statusId = PaymentStatus.Completed.Id;
+        _transactionId = transactionId;
+        _completedAt = DateTime.UtcNow;
+
+        AddDomainEvent(new PaymentCompletedDomainEvent(Id, _orderId, transactionId, _amount, _currency));
+    }
+
+    /// <summary>
+    /// EN: Mark the payment as failed.
+    /// VI: Danh dau thanh toan that bai.
+    /// </summary>
+    /// <param name="errorCode">EN: Error code from gateway / VI: Ma loi tu cong thanh toan</param>
+    /// <param name="errorMessage">EN: Error message / VI: Thong bao loi</param>
+    public void Fail(string? errorCode, string? errorMessage)
+    {
+        if (_statusId != PaymentStatus.Pending.Id && _statusId != PaymentStatus.Processing.Id)
+            throw new WalletDomainException(
+                $"Cannot fail payment from status {Status.Name} / " +
+                $"Khong the danh dau that bai tu trang thai {Status.Name}");
+
+        _statusId = PaymentStatus.Failed.Id;
+        _errorCode = errorCode;
+        _errorMessage = errorMessage;
+        _completedAt = DateTime.UtcNow;
+
+        AddDomainEvent(new PaymentFailedDomainEvent(Id, _orderId, errorCode, errorMessage));
+    }
+
+    /// <summary>
+    /// EN: Refund the payment.
+    /// VI: Hoan tien thanh toan.
+    /// </summary>
+    public void Refund()
+    {
+        if (_statusId != PaymentStatus.Completed.Id)
+            throw new WalletDomainException(
+                $"Can only refund completed payments / " +
+                $"Chi co the hoan tien cac thanh toan da hoan thanh");
+
+        _statusId = PaymentStatus.Refunded.Id;
+    }
+}
--- a/services/wallet-service-net/src/WalletService.Domain/AggregatesModel/PaymentAggregate/PaymentRequest.cs
+++ b/services/wallet-service-net/src/WalletService.Domain/AggregatesModel/PaymentAggregate/PaymentRequest.cs
@@ -0,0 +1,39 @@
+namespace WalletService.Domain.AggregatesModel.PaymentAggregate;
+
+/// <summary>
+/// EN: Value object representing a payment request to a payment gateway.
+/// VI: Value object dai dien cho yeu cau thanh toan den cong thanh toan.
+/// </summary>
+/// <param name="OrderId">EN: The order identifier / VI: Ma don hang</param>
+/// <param name="Amount">EN: Payment amount / VI: So tien thanh toan</param>
+/// <param name="Currency">EN: Currency code (e.g., VND) / VI: Ma tien te (vd: VND)</param>
+/// <param name="Description">EN: Payment description / VI: Mo ta thanh toan</param>
+/// <param name="ReturnUrl">EN: URL to redirect after payment / VI: URL chuyen huong sau thanh toan</param>
+/// <param name="IpAddress">EN: Customer IP address / VI: Dia chi IP khach hang</param>
+public record PaymentRequest(
+    Guid OrderId,
+    decimal Amount,
+    string Currency,
+    string Description,
+    string ReturnUrl,
+    string IpAddress
+);
+
+/// <summary>
+/// EN: Value object representing a payment gateway response.
+/// VI: Value object dai dien cho ket qua tra ve tu cong thanh toan.
+/// </summary>
+/// <param name="Success">EN: Whether the operation succeeded / VI: Thao tac co thanh cong khong</param>
+/// <param name="TransactionId">EN: Gateway transaction identifier / VI: Ma giao dich cong thanh toan</param>
+/// <param name="PaymentUrl">EN: URL to redirect customer for payment / VI: URL chuyen huong khach hang de thanh toan</param>
+/// <param name="ErrorCode">EN: Error code if failed / VI: Ma loi neu that bai</param>
+/// <param name="ErrorMessage">EN: Error message if failed / VI: Thong bao loi neu that bai</param>
+/// <param name="GatewayResponse">EN: Raw gateway response data / VI: Du lieu phan hoi tho tu cong thanh toan</param>
+public record PaymentResult(
+    bool Success,
+    string? TransactionId = null,
+    string? PaymentUrl = null,
+    string? ErrorCode = null,
+    string? ErrorMessage = null,
+    IDictionary<string, string>? GatewayResponse = null
+);
--- a/services/wallet-service-net/src/WalletService.Domain/AggregatesModel/PaymentAggregate/PaymentStatus.cs
+++ b/services/wallet-service-net/src/WalletService.Domain/AggregatesModel/PaymentAggregate/PaymentStatus.cs
@@ -0,0 +1,42 @@
+namespace WalletService.Domain.AggregatesModel.PaymentAggregate;
+
+using WalletService.Domain.SeedWork;
+
+/// <summary>
+/// EN: Payment status enumeration using type-safe enum pattern.
+/// VI: Enumeration trang thai thanh toan su dung pattern enum an toan kieu.
+/// </summary>
+public class PaymentStatus : Enumeration
+{
+    /// <summary>
+    /// EN: Payment has been created but not yet processed.
+    /// VI: Thanh toan da duoc tao nhung chua xu ly.
+    /// </summary>
+    public static PaymentStatus Pending = new(1, nameof(Pending));
+
+    /// <summary>
+    /// EN: Payment is being processed by the gateway.
+    /// VI: Thanh toan dang duoc xu ly boi cong thanh toan.
+    /// </summary>
+    public static PaymentStatus Processing = new(2, nameof(Processing));
+
+    /// <summary>
+    /// EN: Payment has been completed successfully.
+    /// VI: Thanh toan da hoan thanh thanh cong.
+    /// </summary>
+    public static PaymentStatus Completed = new(3, nameof(Completed));
+
+    /// <summary>
+    /// EN: Payment has failed.
+    /// VI: Thanh toan da that bai.
+    /// </summary>
+    public static PaymentStatus Failed = new(4, nameof(Failed));
+
+    /// <summary>
+    /// EN: Payment has been refunded.
+    /// VI: Thanh toan da duoc hoan tien.
+    /// </summary>
+    public static PaymentStatus Refunded = new(5, nameof(Refunded));
+
+    public PaymentStatus(int id, string name) : base(id, name) { }
+}
--- a/services/wallet-service-net/src/WalletService.Domain/Events/PaymentCompletedDomainEvent.cs
+++ b/services/wallet-service-net/src/WalletService.Domain/Events/PaymentCompletedDomainEvent.cs
@@ -0,0 +1,32 @@
+namespace WalletService.Domain.Events;
+
+using MediatR;
+
+/// <summary>
+/// EN: Domain event raised when a payment is completed successfully.
+/// VI: Domain event duoc phat ra khi thanh toan hoan thanh thanh cong.
+/// </summary>
+public class PaymentCompletedDomainEvent : INotification
+{
+    public Guid PaymentId { get; }
+    public Guid OrderId { get; }
+    public string TransactionId { get; }
+    public decimal Amount { get; }
+    public string Currency { get; }
+    public DateTime OccurredAt { get; }
+
+    public PaymentCompletedDomainEvent(
+        Guid paymentId,
+        Guid orderId,
+        string transactionId,
+        decimal amount,
+        string currency)
+    {
+        PaymentId = paymentId;
+        OrderId = orderId;
+        TransactionId = transactionId;
+        Amount = amount;
+        Currency = currency;
+        OccurredAt = DateTime.UtcNow;
+    }
+}
--- a/services/wallet-service-net/src/WalletService.Domain/Events/PaymentCreatedDomainEvent.cs
+++ b/services/wallet-service-net/src/WalletService.Domain/Events/PaymentCreatedDomainEvent.cs
@@ -0,0 +1,32 @@
+namespace WalletService.Domain.Events;
+
+using MediatR;
+
+/// <summary>
+/// EN: Domain event raised when a new payment is created.
+/// VI: Domain event duoc phat ra khi mot thanh toan moi duoc tao.
+/// </summary>
+public class PaymentCreatedDomainEvent : INotification
+{
+    public Guid PaymentId { get; }
+    public Guid OrderId { get; }
+    public decimal Amount { get; }
+    public string Currency { get; }
+    public string GatewayName { get; }
+    public DateTime OccurredAt { get; }
+
+    public PaymentCreatedDomainEvent(
+        Guid paymentId,
+        Guid orderId,
+        decimal amount,
+        string currency,
+        string gatewayName)
+    {
+        PaymentId = paymentId;
+        OrderId = orderId;
+        Amount = amount;
+        Currency = currency;
+        GatewayName = gatewayName;
+        OccurredAt = DateTime.UtcNow;
+    }
+}
--- a/services/wallet-service-net/src/WalletService.Domain/Events/PaymentFailedDomainEvent.cs
+++ b/services/wallet-service-net/src/WalletService.Domain/Events/PaymentFailedDomainEvent.cs
@@ -0,0 +1,29 @@
+namespace WalletService.Domain.Events;
+
+using MediatR;
+
+/// <summary>
+/// EN: Domain event raised when a payment fails.
+/// VI: Domain event duoc phat ra khi thanh toan that bai.
+/// </summary>
+public class PaymentFailedDomainEvent : INotification
+{
+    public Guid PaymentId { get; }
+    public Guid OrderId { get; }
+    public string? ErrorCode { get; }
+    public string? ErrorMessage { get; }
+    public DateTime OccurredAt { get; }
+
+    public PaymentFailedDomainEvent(
+        Guid paymentId,
+        Guid orderId,
+        string? errorCode,
+        string? errorMessage)
+    {
+        PaymentId = paymentId;
+        OrderId = orderId;
+        ErrorCode = errorCode;
+        ErrorMessage = errorMessage;
+        OccurredAt = DateTime.UtcNow;
+    }
+}
--- a/services/wallet-service-net/src/WalletService.Infrastructure/DependencyInjection.cs
+++ b/services/wallet-service-net/src/WalletService.Infrastructure/DependencyInjection.cs
@@ -3,8 +3,10 @@ namespace WalletService.Infrastructure;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
+using WalletService.Domain.AggregatesModel.PaymentAggregate;
 using WalletService.Domain.AggregatesModel.PointAccountAggregate;
 using WalletService.Domain.AggregatesModel.WalletAggregate;
+using WalletService.Infrastructure.PaymentGateways;
 using WalletService.Infrastructure.Repositories;

 /// <summary>
@@ -38,6 +40,13 @@ public static class DependencyInjection
        // VI: Đăng ký repositories
        services.AddScoped<IWalletRepository, WalletRepository>();
        services.AddScoped<IPointAccountRepository, PointAccountRepository>();
+        services.AddScoped<IPaymentRepository, PaymentRepository>();
+
+        // EN: Register VN Pay options and gateway
+        // VI: Đăng ký VN Pay options va gateway
+        services.Configure<VnPayOptions>(configuration.GetSection(VnPayOptions.SectionName));
+        services.AddHttpClient<VnPayGateway>();
+        services.AddScoped<IPaymentGateway, VnPayGateway>();

        return services;
    }
--- a/services/wallet-service-net/src/WalletService.Infrastructure/EntityConfigurations/PaymentEntityTypeConfiguration.cs
+++ b/services/wallet-service-net/src/WalletService.Infrastructure/EntityConfigurations/PaymentEntityTypeConfiguration.cs
@@ -0,0 +1,99 @@
+namespace WalletService.Infrastructure.EntityConfigurations;
+
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+using WalletService.Domain.AggregatesModel.PaymentAggregate;
+
+/// <summary>
+/// EN: EF Core configuration for Payment aggregate.
+/// VI: Cau hinh EF Core cho aggregate Payment.
+/// </summary>
+public class PaymentEntityTypeConfiguration : IEntityTypeConfiguration<Payment>
+{
+    public void Configure(EntityTypeBuilder<Payment> builder)
+    {
+        builder.ToTable("payments");
+
+        builder.HasKey(p => p.Id);
+
+        builder.Property(p => p.Id)
+            .HasColumnName("id")
+            .ValueGeneratedNever();
+
+        builder.Property<Guid>("_orderId")
+            .HasColumnName("order_id")
+            .IsRequired();
+
+        builder.Property<decimal>("_amount")
+            .HasColumnName("amount")
+            .HasPrecision(18, 2)
+            .IsRequired();
+
+        builder.Property<string>("_currency")
+            .HasColumnName("currency")
+            .HasMaxLength(10)
+            .IsRequired();
+
+        builder.Property<string>("_gatewayName")
+            .HasColumnName("gateway_name")
+            .HasMaxLength(50)
+            .IsRequired();
+
+        builder.Property<string?>("_transactionId")
+            .HasColumnName("transaction_id")
+            .HasMaxLength(255);
+
+        builder.Property<string?>("_paymentUrl")
+            .HasColumnName("payment_url")
+            .HasMaxLength(2048);
+
+        builder.Property<int>("_statusId")
+            .HasColumnName("status_id")
+            .IsRequired();
+
+        builder.Property<string?>("_errorCode")
+            .HasColumnName("error_code")
+            .HasMaxLength(50);
+
+        builder.Property<string?>("_errorMessage")
+            .HasColumnName("error_message")
+            .HasMaxLength(500);
+
+        builder.Property<DateTime>("_createdAt")
+            .HasColumnName("created_at")
+            .IsRequired();
+
+        builder.Property<DateTime?>("_completedAt")
+            .HasColumnName("completed_at");
+
+        // EN: Ignore computed properties and domain events
+        // VI: Bo qua cac property tinh toan va domain events
+        builder.Ignore(p => p.OrderId);
+        builder.Ignore(p => p.Amount);
+        builder.Ignore(p => p.Currency);
+        builder.Ignore(p => p.GatewayName);
+        builder.Ignore(p => p.TransactionId);
+        builder.Ignore(p => p.PaymentUrl);
+        builder.Ignore(p => p.StatusId);
+        builder.Ignore(p => p.Status);
+        builder.Ignore(p => p.ErrorCode);
+        builder.Ignore(p => p.ErrorMessage);
+        builder.Ignore(p => p.CreatedAt);
+        builder.Ignore(p => p.CompletedAt);
+        builder.Ignore(p => p.DomainEvents);
+
+        // EN: Indexes for common queries
+        // VI: Index cho cac truy van thuong dung
+        builder.HasIndex("_orderId")
+            .HasDatabaseName("ix_payments_order_id");
+
+        builder.HasIndex("_transactionId")
+            .HasDatabaseName("ix_payments_transaction_id");
+
+        builder.HasIndex("_statusId")
+            .HasDatabaseName("ix_payments_status_id");
+
+        builder.HasIndex("_gatewayName")
+            .HasDatabaseName("ix_payments_gateway_name");
+    }
+}
--- a/services/wallet-service-net/src/WalletService.Infrastructure/PaymentGateways/VnPayGateway.cs
+++ b/services/wallet-service-net/src/WalletService.Infrastructure/PaymentGateways/VnPayGateway.cs
@@ -0,0 +1,326 @@
+namespace WalletService.Infrastructure.PaymentGateways;
+
+using System.Globalization;
+using System.Net.Http.Json;
+using System.Security.Cryptography;
+using System.Text;
+using System.Text.Json;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Options;
+using WalletService.Domain.AggregatesModel.PaymentAggregate;
+
+/// <summary>
+/// EN: VN Pay payment gateway implementation (API v2.1.0).
+/// VI: Trien khai cong thanh toan VN Pay (API v2.1.0).
+/// </summary>
+/// <remarks>
+/// EN: Supports payment creation, query, refund, and IPN callback validation.
+/// Sandbox: https://sandbox.vnpayment.vn/paymentv2/vpcpay.html
+/// VI: Ho tro tao thanh toan, truy van, hoan tien, va xac thuc IPN callback.
+/// Sandbox: https://sandbox.vnpayment.vn/paymentv2/vpcpay.html
+/// </remarks>
+public class VnPayGateway : IPaymentGateway
+{
+    private readonly VnPayOptions _options;
+    private readonly HttpClient _httpClient;
+    private readonly ILogger<VnPayGateway> _logger;
+
+    /// <summary>
+    /// EN: VN Pay API version.
+    /// VI: Phien ban API VN Pay.
+    /// </summary>
+    private const string VnPayVersion = "2.1.0";
+
+    /// <summary>
+    /// EN: VN Pay command for payment.
+    /// VI: Lenh VN Pay cho thanh toan.
+    /// </summary>
+    private const string VnPayCommandPay = "pay";
+
+    /// <summary>
+    /// EN: VN Pay command for query.
+    /// VI: Lenh VN Pay cho truy van.
+    /// </summary>
+    private const string VnPayCommandQuery = "querydr";
+
+    /// <summary>
+    /// EN: VN Pay command for refund.
+    /// VI: Lenh VN Pay cho hoan tien.
+    /// </summary>
+    private const string VnPayCommandRefund = "refund";
+
+    public string GatewayName => "VNPAY";
+
+    public VnPayGateway(
+        IOptions<VnPayOptions> options,
+        HttpClient httpClient,
+        ILogger<VnPayGateway> logger)
+    {
+        _options = options.Value ?? throw new ArgumentNullException(nameof(options));
+        _httpClient = httpClient ?? throw new ArgumentNullException(nameof(httpClient));
+        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
+    }
+
+    /// <inheritdoc />
+    public Task<PaymentResult> CreatePaymentAsync(PaymentRequest request, CancellationToken cancellationToken)
+    {
+        _logger.LogInformation(
+            "EN: Creating VN Pay payment for order {OrderId}, amount {Amount} {Currency} / " +
+            "VI: Tao thanh toan VN Pay cho don hang {OrderId}, so tien {Amount} {Currency}",
+            request.OrderId, request.Amount, request.Currency);
+
+        var vnpParams = new SortedDictionary<string, string>
+        {
+            { "vnp_Version", VnPayVersion },
+            { "vnp_Command", VnPayCommandPay },
+            { "vnp_TmnCode", _options.TmnCode },
+            { "vnp_Amount", ((long)(request.Amount * 100)).ToString() },
+            { "vnp_CreateDate", DateTime.UtcNow.ToString("yyyyMMddHHmmss") },
+            { "vnp_CurrCode", request.Currency.ToUpperInvariant() },
+            { "vnp_IpAddr", request.IpAddress },
+            { "vnp_Locale", "vn" },
+            { "vnp_OrderInfo", request.Description },
+            { "vnp_OrderType", "other" },
+            { "vnp_ReturnUrl", request.ReturnUrl },
+            { "vnp_TxnRef", request.OrderId.ToString("N") },
+            { "vnp_ExpireDate", DateTime.UtcNow.AddMinutes(15).ToString("yyyyMMddHHmmss") }
+        };
+
+        // EN: Build query string and generate HMAC-SHA512 hash
+        // VI: Xay dung query string va tao hash HMAC-SHA512
+        var queryString = BuildQueryString(vnpParams);
+        var secureHash = ComputeHmacSha512(_options.HashSecret, queryString);
+
+        var paymentUrl = $"{_options.PaymentUrl}?{queryString}&vnp_SecureHash={secureHash}";
+
+        _logger.LogInformation(
+            "EN: VN Pay payment URL generated for order {OrderId} / " +
+            "VI: Da tao URL thanh toan VN Pay cho don hang {OrderId}",
+            request.OrderId);
+
+        return Task.FromResult(new PaymentResult(
+            Success: true,
+            TransactionId: request.OrderId.ToString("N"),
+            PaymentUrl: paymentUrl
+        ));
+    }
+
+    /// <inheritdoc />
+    public async Task<PaymentResult> QueryPaymentAsync(string transactionId, CancellationToken cancellationToken)
+    {
+        _logger.LogInformation(
+            "EN: Querying VN Pay transaction {TransactionId} / " +
+            "VI: Truy van giao dich VN Pay {TransactionId}",
+            transactionId);
+
+        var requestDate = DateTime.UtcNow.ToString("yyyyMMddHHmmss");
+        var requestId = Guid.NewGuid().ToString("N");
+
+        var vnpParams = new SortedDictionary<string, string>
+        {
+            { "vnp_RequestId", requestId },
+            { "vnp_Version", VnPayVersion },
+            { "vnp_Command", VnPayCommandQuery },
+            { "vnp_TmnCode", _options.TmnCode },
+            { "vnp_TxnRef", transactionId },
+            { "vnp_OrderInfo", $"Query transaction {transactionId}" },
+            { "vnp_TransactionDate", requestDate },
+            { "vnp_CreateDate", requestDate },
+            { "vnp_IpAddr", "127.0.0.1" }
+        };
+
+        // EN: Generate hash for query request
+        // VI: Tao hash cho yeu cau truy van
+        var hashData = $"{requestId}|{VnPayVersion}|{VnPayCommandQuery}|{_options.TmnCode}|{transactionId}|{requestDate}|{requestDate}|127.0.0.1|Query transaction {transactionId}";
+        var secureHash = ComputeHmacSha512(_options.HashSecret, hashData);
+        vnpParams.Add("vnp_SecureHash", secureHash);
+
+        try
+        {
+            var response = await _httpClient.PostAsJsonAsync(
+                _options.ApiUrl,
+                vnpParams,
+                cancellationToken);
+
+            if (!response.IsSuccessStatusCode)
+            {
+                _logger.LogWarning(
+                    "EN: VN Pay query failed with status {StatusCode} / " +
+                    "VI: Truy van VN Pay that bai voi status {StatusCode}",
+                    response.StatusCode);
+
+                return new PaymentResult(
+                    Success: false,
+                    ErrorCode: "QUERY_FAILED",
+                    ErrorMessage: $"VN Pay query returned HTTP {(int)response.StatusCode}");
+            }
+
+            var content = await response.Content.ReadAsStringAsync(cancellationToken);
+            var responseData = JsonSerializer.Deserialize<Dictionary<string, string>>(content);
+
+            var responseCode = responseData?.GetValueOrDefault("vnp_ResponseCode") ?? "99";
+            var isSuccess = responseCode == "00";
+
+            return new PaymentResult(
+                Success: isSuccess,
+                TransactionId: responseData?.GetValueOrDefault("vnp_TransactionNo"),
+                ErrorCode: isSuccess ? null : responseCode,
+                ErrorMessage: isSuccess ? null : $"VN Pay response code: {responseCode}",
+                GatewayResponse: responseData?.ToDictionary(k => k.Key, v => v.Value));
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex,
+                "EN: Error querying VN Pay transaction {TransactionId} / " +
+                "VI: Loi truy van giao dich VN Pay {TransactionId}",
+                transactionId);
+
+            return new PaymentResult(
+                Success: false,
+                ErrorCode: "QUERY_ERROR",
+                ErrorMessage: ex.Message);
+        }
+    }
+
+    /// <inheritdoc />
+    public async Task<PaymentResult> RefundAsync(string transactionId, decimal amount, CancellationToken cancellationToken)
+    {
+        _logger.LogInformation(
+            "EN: Requesting VN Pay refund for transaction {TransactionId}, amount {Amount} / " +
+            "VI: Yeu cau hoan tien VN Pay cho giao dich {TransactionId}, so tien {Amount}",
+            transactionId, amount);
+
+        var requestDate = DateTime.UtcNow.ToString("yyyyMMddHHmmss");
+        var requestId = Guid.NewGuid().ToString("N");
+
+        var vnpParams = new SortedDictionary<string, string>
+        {
+            { "vnp_RequestId", requestId },
+            { "vnp_Version", VnPayVersion },
+            { "vnp_Command", VnPayCommandRefund },
+            { "vnp_TmnCode", _options.TmnCode },
+            { "vnp_TransactionType", "02" }, // Full refund
+            { "vnp_TxnRef", transactionId },
+            { "vnp_Amount", ((long)(amount * 100)).ToString() },
+            { "vnp_OrderInfo", $"Refund transaction {transactionId}" },
+            { "vnp_TransactionDate", requestDate },
+            { "vnp_CreateDate", requestDate },
+            { "vnp_IpAddr", "127.0.0.1" }
+        };
+
+        // EN: Generate hash for refund request
+        // VI: Tao hash cho yeu cau hoan tien
+        var hashData = $"{requestId}|{VnPayVersion}|{VnPayCommandRefund}|{_options.TmnCode}|02|{transactionId}|{(long)(amount * 100)}|0|{requestDate}|{requestDate}|127.0.0.1|Refund transaction {transactionId}";
+        var secureHash = ComputeHmacSha512(_options.HashSecret, hashData);
+        vnpParams.Add("vnp_SecureHash", secureHash);
+
+        try
+        {
+            var response = await _httpClient.PostAsJsonAsync(
+                _options.ApiUrl,
+                vnpParams,
+                cancellationToken);
+
+            if (!response.IsSuccessStatusCode)
+            {
+                return new PaymentResult(
+                    Success: false,
+                    ErrorCode: "REFUND_FAILED",
+                    ErrorMessage: $"VN Pay refund returned HTTP {(int)response.StatusCode}");
+            }
+
+            var content = await response.Content.ReadAsStringAsync(cancellationToken);
+            var responseData = JsonSerializer.Deserialize<Dictionary<string, string>>(content);
+
+            var responseCode = responseData?.GetValueOrDefault("vnp_ResponseCode") ?? "99";
+            var isSuccess = responseCode == "00";
+
+            return new PaymentResult(
+                Success: isSuccess,
+                TransactionId: responseData?.GetValueOrDefault("vnp_TransactionNo"),
+                ErrorCode: isSuccess ? null : responseCode,
+                ErrorMessage: isSuccess ? null : $"VN Pay refund response code: {responseCode}",
+                GatewayResponse: responseData?.ToDictionary(k => k.Key, v => v.Value));
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex,
+                "EN: Error requesting VN Pay refund for transaction {TransactionId} / " +
+                "VI: Loi yeu cau hoan tien VN Pay cho giao dich {TransactionId}",
+                transactionId);
+
+            return new PaymentResult(
+                Success: false,
+                ErrorCode: "REFUND_ERROR",
+                ErrorMessage: ex.Message);
+        }
+    }
+
+    /// <inheritdoc />
+    public bool ValidateCallback(IDictionary<string, string> parameters, string secureHash)
+    {
+        _logger.LogInformation(
+            "EN: Validating VN Pay IPN callback / " +
+            "VI: Xac thuc VN Pay IPN callback");
+
+        // EN: Remove the secure hash from parameters before verification
+        // VI: Loai bo secure hash khoi cac tham so truoc khi xac thuc
+        var vnpParams = new SortedDictionary<string, string>(
+            parameters
+                .Where(p => p.Key.StartsWith("vnp_") &&
+                           p.Key != "vnp_SecureHash" &&
+                           p.Key != "vnp_SecureHashType")
+                .ToDictionary(p => p.Key, p => p.Value));
+
+        var queryString = BuildQueryString(vnpParams);
+        var computedHash = ComputeHmacSha512(_options.HashSecret, queryString);
+
+        var isValid = string.Equals(computedHash, secureHash, StringComparison.OrdinalIgnoreCase);
+
+        if (!isValid)
+        {
+            _logger.LogWarning(
+                "EN: VN Pay IPN callback hash validation failed / " +
+                "VI: Xac thuc hash IPN callback VN Pay that bai");
+        }
+
+        return isValid;
+    }
+
+    #region Private Helpers
+
+    /// <summary>
+    /// EN: Build URL-encoded query string from sorted parameters.
+    /// VI: Xay dung query string duoc URL-encode tu cac tham so da sap xep.
+    /// </summary>
+    private static string BuildQueryString(SortedDictionary<string, string> parameters)
+    {
+        var sb = new StringBuilder();
+        foreach (var kvp in parameters)
+        {
+            if (sb.Length > 0)
+                sb.Append('&');
+            sb.Append(Uri.EscapeDataString(kvp.Key));
+            sb.Append('=');
+            sb.Append(Uri.EscapeDataString(kvp.Value));
+        }
+        return sb.ToString();
+    }
+
+    /// <summary>
+    /// EN: Compute HMAC-SHA512 hash.
+    /// VI: Tinh toan hash HMAC-SHA512.
+    /// </summary>
+    private static string ComputeHmacSha512(string key, string data)
+    {
+        var keyBytes = Encoding.UTF8.GetBytes(key);
+        var dataBytes = Encoding.UTF8.GetBytes(data);
+
+        using var hmac = new HMACSHA512(keyBytes);
+        var hashBytes = hmac.ComputeHash(dataBytes);
+
+        return Convert.ToHexStringLower(hashBytes);
+    }
+
+    #endregion
+}
--- a/services/wallet-service-net/src/WalletService.Infrastructure/PaymentGateways/VnPayOptions.cs
+++ b/services/wallet-service-net/src/WalletService.Infrastructure/PaymentGateways/VnPayOptions.cs
@@ -0,0 +1,44 @@
+namespace WalletService.Infrastructure.PaymentGateways;
+
+/// <summary>
+/// EN: Configuration options for VN Pay payment gateway.
+/// VI: Cac tuy chon cau hinh cho cong thanh toan VN Pay.
+/// </summary>
+public class VnPayOptions
+{
+    /// <summary>
+    /// EN: Configuration section name.
+    /// VI: Ten section cau hinh.
+    /// </summary>
+    public const string SectionName = "VnPay";
+
+    /// <summary>
+    /// EN: Merchant terminal code assigned by VN Pay.
+    /// VI: Ma terminal merchant duoc VN Pay cap.
+    /// </summary>
+    public string TmnCode { get; set; } = string.Empty;
+
+    /// <summary>
+    /// EN: Secret key for HMAC-SHA512 hash generation.
+    /// VI: Khoa bi mat de tao hash HMAC-SHA512.
+    /// </summary>
+    public string HashSecret { get; set; } = string.Empty;
+
+    /// <summary>
+    /// EN: VN Pay payment URL (sandbox or production).
+    /// VI: URL thanh toan VN Pay (sandbox hoac production).
+    /// </summary>
+    public string PaymentUrl { get; set; } = "https://sandbox.vnpayment.vn/paymentv2/vpcpay.html";
+
+    /// <summary>
+    /// EN: Return URL after payment completion.
+    /// VI: URL tra ve sau khi hoan thanh thanh toan.
+    /// </summary>
+    public string ReturnUrl { get; set; } = string.Empty;
+
+    /// <summary>
+    /// EN: VN Pay API URL for querying transaction status.
+    /// VI: URL API VN Pay de truy van trang thai giao dich.
+    /// </summary>
+    public string ApiUrl { get; set; } = "https://sandbox.vnpayment.vn/merchant_webapi/api/transaction";
+}
--- a/services/wallet-service-net/src/WalletService.Infrastructure/Repositories/PaymentRepository.cs
+++ b/services/wallet-service-net/src/WalletService.Infrastructure/Repositories/PaymentRepository.cs
@@ -0,0 +1,64 @@
+namespace WalletService.Infrastructure.Repositories;
+
+using Microsoft.EntityFrameworkCore;
+using WalletService.Domain.AggregatesModel.PaymentAggregate;
+using WalletService.Domain.SeedWork;
+
+/// <summary>
+/// EN: Repository implementation for Payment aggregate.
+/// VI: Repository implementation cho aggregate Payment.
+/// </summary>
+public class PaymentRepository : IPaymentRepository
+{
+    private readonly WalletServiceContext _context;
+
+    public IUnitOfWork UnitOfWork => _context;
+
+    public PaymentRepository(WalletServiceContext context)
+    {
+        _context = context ?? throw new ArgumentNullException(nameof(context));
+    }
+
+    /// <inheritdoc />
+    public async Task<Payment?> GetByIdAsync(Guid paymentId)
+    {
+        return await _context.Payments
+            .FirstOrDefaultAsync(p => p.Id == paymentId);
+    }
+
+    /// <inheritdoc />
+    public async Task<Payment?> GetByOrderIdAsync(Guid orderId)
+    {
+        return await _context.Payments
+            .OrderByDescending(p => p.CreatedAt)
+            .FirstOrDefaultAsync(p => p.OrderId == orderId);
+    }
+
+    /// <inheritdoc />
+    public async Task<Payment?> GetByTransactionIdAsync(string transactionId)
+    {
+        return await _context.Payments
+            .FirstOrDefaultAsync(p => p.TransactionId == transactionId);
+    }
+
+    /// <inheritdoc />
+    public async Task<IEnumerable<Payment>> GetPaymentsByOrderIdAsync(Guid orderId)
+    {
+        return await _context.Payments
+            .Where(p => p.OrderId == orderId)
+            .OrderByDescending(p => p.CreatedAt)
+            .ToListAsync();
+    }
+
+    /// <inheritdoc />
+    public Payment Add(Payment payment)
+    {
+        return _context.Payments.Add(payment).Entity;
+    }
+
+    /// <inheritdoc />
+    public void Update(Payment payment)
+    {
+        _context.Entry(payment).State = EntityState.Modified;
+    }
+}
--- a/services/wallet-service-net/src/WalletService.Infrastructure/WalletServiceContext.cs
+++ b/services/wallet-service-net/src/WalletService.Infrastructure/WalletServiceContext.cs
@@ -3,6 +3,7 @@ namespace WalletService.Infrastructure;
 using MediatR;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.EntityFrameworkCore.Storage;
+using WalletService.Domain.AggregatesModel.PaymentAggregate;
 using WalletService.Domain.AggregatesModel.PointAccountAggregate;
 using WalletService.Domain.AggregatesModel.WalletAggregate;
 using WalletService.Domain.SeedWork;
@@ -20,6 +21,7 @@ public class WalletServiceContext : DbContext, IUnitOfWork
    public DbSet<WalletItem> WalletItems { get; set; } = null!;
    public DbSet<WalletTransaction> WalletTransactions { get; set; } = null!;
    public DbSet<HoldItem> WalletHolds { get; set; } = null!;
+    public DbSet<Payment> Payments { get; set; } = null!;
    public DbSet<PointAccount> PointAccounts { get; set; } = null!;
    public DbSet<PointTransaction> PointTransactions { get; set; } = null!;