outbox checkpoint

.files/mccn-realm-export.json

@@ -70,10 +70,10 @@
       "username": "service-account-mccn-api",
       "enabled": true,
       "serviceAccountClientId": "mccn-api",
-      "clientRoleMappings": {
+      "clientRoles": {
         "realm-management": [
-          { "name": "manage-users" },
+          "manage-users",
-          { "name": "view-users" }
+          "view-users"
         ]
       }
     }

Mccn.slnx

@@ -12,21 +12,18 @@
     <Folder Name="/src/Modules/" />
     <Folder Name="/src/Modules/Hello/">
         <Project Path="src/Modules/Hello/Mccn.Modules.Hello.Application/Mccn.Modules.Hello.Application.csproj" />
-        <Project
+        <Project Path="src/Modules/Hello/Mccn.Modules.Hello.ArchitectureTests/Mccn.Modules.Hello.ArchitectureTests.csproj" />
-                Path="src/Modules/Hello/Mccn.Modules.Hello.ArchitectureTests/Mccn.Modules.Hello.ArchitectureTests.csproj"/>
         <Project Path="src/Modules/Hello/Mccn.Modules.Hello.Infrastructure/Mccn.Modules.Hello.Infrastructure.csproj" />
-        <Project
+        <Project Path="src/Modules/Hello/Mccn.Modules.Hello.IntegrationTests/Mccn.Modules.Hello.IntegrationTests.csproj" />
-                Path="src/Modules/Hello/Mccn.Modules.Hello.IntegrationTests/Mccn.Modules.Hello.IntegrationTests.csproj"/>
         <Project Path="src/Modules/Hello/Mccn.Modules.Hello.Presentation/Mccn.Modules.Hello.Presentation.csproj" />
     </Folder>
     <Folder Name="/src/Modules/Users/">
         <Project Path="src/Modules/Users/Mccn.Modules.Users.Application/Mccn.Modules.Users.Application.csproj" />
-        <Project
+        <Project Path="src/Modules/Users/Mccn.Modules.Users.ArchitectureTests/Mccn.Modules.Users.ArchitectureTests.csproj" />
-                Path="src/Modules/Users/Mccn.Modules.Users.ArchitectureTests/Mccn.Modules.Users.ArchitectureTests.csproj"/>
         <Project Path="src/Modules/Users/Mccn.Modules.Users.Domain/Mccn.Modules.Users.Domain.csproj" />
         <Project Path="src/Modules/Users/Mccn.Modules.Users.Infrastructure/Mccn.Modules.Users.Infrastructure.csproj" />
-        <Project
+        <Project Path="src/Modules/Users/Mccn.Modules.Users.IntegrationEvents/Mccn.Modules.Users.IntegrationEvents.csproj" />
-                Path="src/Modules/Users/Mccn.Modules.Users.IntegrationTests/Mccn.Modules.Users.IntegrationTests.csproj"/>
+        <Project Path="src/Modules/Users/Mccn.Modules.Users.IntegrationTests/Mccn.Modules.Users.IntegrationTests.csproj" />
         <Project Path="src/Modules/Users/Mccn.Modules.Users.Presentation/Mccn.Modules.Users.Presentation.csproj" />
         <Project Path="src/Modules/Users/Mccn.Modules.Users.UnitTests/Mccn.Modules.Users.UnitTests.csproj" />
     </Folder>

docker-compose.yml

@@ -42,6 +42,18 @@ services:
     ports:
       - 6379:6379
 
+  mccn.queue:
+    image: rabbitmq:4-management
+    container_name: mccn.queue
+    environment:
+      RABBITMQ_DEFAULT_USER: guest
+      RABBITMQ_DEFAULT_PASS: guest
+    volumes:
+      - ./.containers/queue:/var/lib/rabbitmq
+    ports:
+      - 5672:5672
+      - 15672:15672
+
   mccn.jaeger:
     image: jaegertracing/all-in-one:latest
     container_name: mccn.jaeger

src/API/Mccn.Api/Extensions/MigrationExtensions.cs

@@ -1,3 +1,4 @@
+using Mccn.Modules.Hello.Infrastructure.Database;
 using Mccn.Modules.Users.Infrastructure.Database;
 using Microsoft.EntityFrameworkCore;
 
@@ -9,6 +10,7 @@ internal static class MigrationExtensions
     {
         using IServiceScope scope = app.Services.CreateScope();
         await MigrateAsync<UsersDbContext>(scope.ServiceProvider);
+        await MigrateAsync<HelloDbContext>(scope.ServiceProvider);
     }
 
     private static async Task MigrateAsync<TContext>(IServiceProvider serviceProvider) where TContext : DbContext

src/API/Mccn.Api/Mccn.Api.http

@@ -43,10 +43,10 @@ POST {{baseAddress}}/users/register
 Content-Type: {{content_type}}
 
 {
-  "email": "user@example.com",
+  "email": "andrej+test6@mccn.dev",
-  "firstName": "Jane",
+  "firstName": "Andrej",
-  "lastName": "Doe",
+  "lastName": "Jovanovic",
-  "password": "Test1234!@#$anin149141"
+  "password": "BestOfTheBest123"
 }
 
 ### Get user profile (requires auth)
@@ -68,3 +68,8 @@ GET {{baseAddress}}/hello?name=World
 ### Say hello to the authenticated user (requires auth)
 GET {{baseAddress}}/hello/me
 Authorization: Bearer {{token}}
+
+### Get welcomed users — lists every user the Hello module was notified about via the inbox.
+# Register a user first (see above), wait ~10 seconds for the outbox and inbox jobs to run,
+# then call this endpoint to confirm the integration event was received and processed.
+GET {{baseAddress}}/hello/welcomed-users

src/API/Mccn.Api/Program.cs

@@ -17,7 +17,10 @@ builder.Host.UseSerilog((context, config) => { config.ReadFrom.Configuration(con
 builder.Services.AddEndpointsApiExplorer();
 builder.Services.AddSwaggerGen();
 
-builder.Services.AddInfrastructure(builder.Configuration);
+builder.Services.AddInfrastructure(
+    builder.Configuration,
+    Mccn.Modules.Users.Infrastructure.DependencyInjection.ConfigureConsumers,
+    Mccn.Modules.Hello.Infrastructure.DependencyInjection.ConfigureConsumers);
 
 builder.Services.AddApplication(
     typeof(RegisterUserCommand).Assembly,

src/Common/Mccn.Common.Application/DependencyInjection.cs

@@ -1,6 +1,7 @@
 using System.Reflection;
 using FluentValidation;
 using Mccn.Common.Application.Behaviors;
+using Mccn.Common.Application.EventBus;
 using MediatR;
 using Microsoft.Extensions.DependencyInjection;
 
@@ -18,6 +19,24 @@ public static class DependencyInjection
 
         services.AddTransient(typeof(IPipelineBehavior<,>), typeof(ValidationBehavior<,>));
 
+        RegisterDomainEventHandlers(services, moduleAssemblies);
+
         return services;
     }
+
+    private static void RegisterDomainEventHandlers(IServiceCollection services, Assembly[] assemblies)
+    {
+        foreach (Assembly assembly in assemblies)
+        {
+            IEnumerable<(Type Implementation, Type Interface)> handlers = assembly.GetTypes()
+                .Where(t => !t.IsAbstract && !t.IsInterface)
+                .SelectMany(t => t.GetInterfaces()
+                    .Where(i => i.IsGenericType &&
+                                i.GetGenericTypeDefinition() == typeof(IDomainEventHandler<>))
+                    .Select(i => (Implementation: t, Interface: i)));
+
+            foreach ((Type implementation, Type iface) in handlers)
+                services.AddTransient(iface, implementation);
+        }
+    }
 }

src/Common/Mccn.Common.Application/EventBus/DomainEventHandler.cs

@@ -0,0 +1,12 @@
+using Mccn.Common.Domain.Abstractions;
+
+namespace Mccn.Common.Application.EventBus;
+
+public abstract class DomainEventHandler<TDomainEvent> : IDomainEventHandler<TDomainEvent>
+    where TDomainEvent : IDomainEvent
+{
+    public abstract Task Handle(TDomainEvent domainEvent, CancellationToken cancellationToken);
+
+    Task IDomainEventHandler.Handle(IDomainEvent domainEvent, CancellationToken cancellationToken) =>
+        Handle((TDomainEvent)domainEvent, cancellationToken);
+}

src/Common/Mccn.Common.Application/EventBus/IDomainEventHandler.cs

@@ -0,0 +1,14 @@
+using Mccn.Common.Domain.Abstractions;
+
+namespace Mccn.Common.Application.EventBus;
+
+public interface IDomainEventHandler
+{
+    Task Handle(IDomainEvent domainEvent, CancellationToken cancellationToken);
+}
+
+public interface IDomainEventHandler<in TDomainEvent> : IDomainEventHandler
+    where TDomainEvent : IDomainEvent
+{
+    Task Handle(TDomainEvent domainEvent, CancellationToken cancellationToken);
+}

src/Common/Mccn.Common.Application/EventBus/IEventBus.cs

@@ -0,0 +1,7 @@
+namespace Mccn.Common.Application.EventBus;
+
+public interface IEventBus
+{
+    Task PublishAsync<T>(T integrationEvent, CancellationToken cancellationToken = default)
+        where T : IIntegrationEvent;
+}

src/Common/Mccn.Common.Application/EventBus/IIntegrationEvent.cs

@@ -0,0 +1,7 @@
+namespace Mccn.Common.Application.EventBus;
+
+public interface IIntegrationEvent
+{
+    Guid Id { get; }
+    DateTime OccurredOnUtc { get; }
+}

src/Common/Mccn.Common.Application/EventBus/IIntegrationEventHandler.cs

@@ -0,0 +1,12 @@
+namespace Mccn.Common.Application.EventBus;
+
+public interface IIntegrationEventHandler
+{
+    Task Handle(IIntegrationEvent integrationEvent, CancellationToken cancellationToken);
+}
+
+public interface IIntegrationEventHandler<in TIntegrationEvent> : IIntegrationEventHandler
+    where TIntegrationEvent : IIntegrationEvent
+{
+    Task Handle(TIntegrationEvent integrationEvent, CancellationToken cancellationToken);
+}

src/Common/Mccn.Common.Application/EventBus/IntegrationEvent.cs

@@ -0,0 +1,3 @@
+namespace Mccn.Common.Application.EventBus;
+
+public abstract record IntegrationEvent(Guid Id, DateTime OccurredOnUtc) : IIntegrationEvent;

src/Common/Mccn.Common.Application/EventBus/IntegrationEventHandler.cs

@@ -0,0 +1,10 @@
+namespace Mccn.Common.Application.EventBus;
+
+public abstract class IntegrationEventHandler<TIntegrationEvent> : IIntegrationEventHandler<TIntegrationEvent>
+    where TIntegrationEvent : IIntegrationEvent
+{
+    public abstract Task Handle(TIntegrationEvent integrationEvent, CancellationToken cancellationToken);
+
+    Task IIntegrationEventHandler.Handle(IIntegrationEvent integrationEvent, CancellationToken cancellationToken) =>
+        Handle((TIntegrationEvent)integrationEvent, cancellationToken);
+}

src/Common/Mccn.Common.Domain/Abstractions/DomainEvent.cs

@@ -0,0 +1,3 @@
+namespace Mccn.Common.Domain.Abstractions;
+
+public abstract record DomainEvent(Guid Id, DateTime OccurredOnUtc) : IDomainEvent;

src/Common/Mccn.Common.Domain/Abstractions/Entity.cs

@@ -2,6 +2,8 @@ namespace Mccn.Common.Domain.Abstractions;
 
 public abstract class Entity
 {
+    private readonly List<IDomainEvent> _domainEvents = [];
+
     protected Entity(Guid id)
     {
         Id = id;
@@ -12,4 +14,10 @@ public abstract class Entity
     }
 
     public Guid Id { get; init; }
+
+    public IReadOnlyList<IDomainEvent> DomainEvents => _domainEvents.AsReadOnly();
+
+    protected void RaiseDomainEvent(IDomainEvent domainEvent) => _domainEvents.Add(domainEvent);
+
+    public void ClearDomainEvents() => _domainEvents.Clear();
 }

src/Common/Mccn.Common.Domain/Abstractions/IDomainEvent.cs

@@ -0,0 +1,7 @@
+namespace Mccn.Common.Domain.Abstractions;
+
+public interface IDomainEvent
+{
+    Guid Id { get; }
+    DateTime OccurredOnUtc { get; }
+}

src/Common/Mccn.Common.Infrastructure/DependencyInjection.cs

@@ -1,9 +1,13 @@
+using MassTransit;
+using Mccn.Common.Application.EventBus;
 using Mccn.Common.Infrastructure.Authentication;
 using Mccn.Common.Infrastructure.Caching;
+using Mccn.Common.Infrastructure.EventBus;
 using Mccn.Common.Infrastructure.ExceptionHandlers;
 using Mccn.Common.Infrastructure.Observability;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
+using Quartz;
 
 namespace Mccn.Common.Infrastructure;
 
@@ -11,7 +15,8 @@ public static class DependencyInjection
 {
     public static IServiceCollection AddInfrastructure(
         this IServiceCollection services,
-        IConfiguration configuration)
+        IConfiguration configuration,
+        params Action<IRegistrationConfigurator>[] moduleConsumers)
     {
         services.AddJwtAuthentication(configuration);
 
@@ -26,6 +31,24 @@ public static class DependencyInjection
 
         services.AddHttpContextAccessor();
 
+        services.AddMassTransit(configure =>
+        {
+            foreach (Action<IRegistrationConfigurator> configureConsumers in moduleConsumers)
+                configureConsumers(configure);
+
+            configure.SetKebabCaseEndpointNameFormatter();
+            configure.UsingRabbitMq((context, cfg) =>
+            {
+                cfg.Host(configuration.GetConnectionString("MessageBroker"));
+                cfg.ConfigureEndpoints(context);
+            });
+        });
+
+        services.AddScoped<IEventBus, EventBus.EventBus>();
+
+        services.AddQuartz();
+        services.AddQuartzHostedService(options => options.WaitForJobsToComplete = true);
+
         return services;
     }
 }

src/Common/Mccn.Common.Infrastructure/EventBus/EventBus.cs

@@ -0,0 +1,13 @@
+using MassTransit;
+using Mccn.Common.Application.EventBus;
+
+namespace Mccn.Common.Infrastructure.EventBus;
+
+internal sealed class EventBus(IBus bus) : IEventBus
+{
+    public async Task PublishAsync<T>(T integrationEvent, CancellationToken cancellationToken = default)
+        where T : IIntegrationEvent
+    {
+        await bus.Publish(integrationEvent, cancellationToken);
+    }
+}

src/Common/Mccn.Common.Infrastructure/Inbox/InboxMessage.cs

@@ -0,0 +1,11 @@
+namespace Mccn.Common.Infrastructure.Inbox;
+
+public sealed class InboxMessage
+{
+    public Guid Id { get; init; }
+    public string Type { get; init; } = string.Empty;
+    public string Content { get; init; } = string.Empty;
+    public DateTime OccurredOnUtc { get; init; }
+    public DateTime? ProcessedOnUtc { get; set; }
+    public string? Error { get; set; }
+}

src/Common/Mccn.Common.Infrastructure/Inbox/InboxMessageConsumer.cs

@@ -0,0 +1,7 @@
+namespace Mccn.Common.Infrastructure.Inbox;
+
+public sealed class InboxMessageConsumer
+{
+    public Guid InboxMessageId { get; init; }
+    public string Name { get; init; } = string.Empty;
+}

src/Common/Mccn.Common.Infrastructure/Mccn.Common.Infrastructure.csproj

@@ -10,12 +10,16 @@
     </ItemGroup>
 
     <ItemGroup>
+        <PackageReference Include="MassTransit" Version="8.3.7"/>
+        <PackageReference Include="MassTransit.RabbitMQ" Version="8.3.7"/>
+        <PackageReference Include="Microsoft.EntityFrameworkCore" Version="10.0.4"/>
         <PackageReference Include="Microsoft.AspNetCore.Authentication.JwtBearer" Version="10.0.5"/>
         <PackageReference Include="Microsoft.Extensions.Caching.StackExchangeRedis" Version="10.0.5"/>
         <PackageReference Include="OpenTelemetry.Exporter.OpenTelemetryProtocol" Version="1.15.0"/>
         <PackageReference Include="OpenTelemetry.Extensions.Hosting" Version="1.15.0"/>
         <PackageReference Include="OpenTelemetry.Instrumentation.AspNetCore" Version="1.15.1"/>
         <PackageReference Include="OpenTelemetry.Instrumentation.Http" Version="1.15.0"/>
+        <PackageReference Include="Quartz.Extensions.Hosting" Version="3.14.0"/>
         <PackageReference Include="Serilog.AspNetCore" Version="10.0.0"/>
         <PackageReference Include="Serilog.Sinks.Seq" Version="9.0.0"/>
     </ItemGroup>

src/Common/Mccn.Common.Infrastructure/Observability/ObservabilityExtensions.cs

@@ -19,6 +19,7 @@ public static class ObservabilityExtensions
                 tracing
                     .AddAspNetCoreInstrumentation()
                     .AddHttpClientInstrumentation()
+                    .AddSource("MassTransit")
                     .AddOtlpExporter(options =>
                     {
                         options.Endpoint = new Uri(

src/Common/Mccn.Common.Infrastructure/Outbox/InsertOutboxMessagesInterceptor.cs

@@ -0,0 +1,43 @@
+using System.Text.Json;
+using Mccn.Common.Domain.Abstractions;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Diagnostics;
+
+namespace Mccn.Common.Infrastructure.Outbox;
+
+public sealed class InsertOutboxMessagesInterceptor : SaveChangesInterceptor
+{
+    public override ValueTask<InterceptionResult<int>> SavingChangesAsync(
+        DbContextEventData eventData,
+        InterceptionResult<int> result,
+        CancellationToken cancellationToken = default)
+    {
+        if (eventData.Context is not null)
+            InsertOutboxMessages(eventData.Context);
+
+        return base.SavingChangesAsync(eventData, result, cancellationToken);
+    }
+
+    private static void InsertOutboxMessages(DbContext context)
+    {
+        List<OutboxMessage> outboxMessages = context.ChangeTracker
+            .Entries<Entity>()
+            .Select(e => e.Entity)
+            .SelectMany(entity =>
+            {
+                IReadOnlyList<IDomainEvent> domainEvents = entity.DomainEvents;
+                entity.ClearDomainEvents();
+                return domainEvents;
+            })
+            .Select(domainEvent => new OutboxMessage
+            {
+                Id = domainEvent.Id,
+                Type = domainEvent.GetType().Name,
+                Content = JsonSerializer.Serialize(domainEvent, domainEvent.GetType()),
+                OccurredOnUtc = domainEvent.OccurredOnUtc
+            })
+            .ToList();
+
+        context.Set<OutboxMessage>().AddRange(outboxMessages);
+    }
+}

src/Common/Mccn.Common.Infrastructure/Outbox/OutboxMessage.cs

@@ -0,0 +1,11 @@
+namespace Mccn.Common.Infrastructure.Outbox;
+
+public sealed class OutboxMessage
+{
+    public Guid Id { get; init; }
+    public string Type { get; init; } = string.Empty;
+    public string Content { get; init; } = string.Empty;
+    public DateTime OccurredOnUtc { get; init; }
+    public DateTime? ProcessedOnUtc { get; set; }
+    public string? Error { get; set; }
+}

src/Modules/Hello/Mccn.Modules.Hello.Application/Abstractions/IUnitOfWork.cs

@@ -0,0 +1,6 @@
+namespace Mccn.Modules.Hello.Application.Abstractions;
+
+public interface IUnitOfWork
+{
+    Task SaveChangesAsync(CancellationToken cancellationToken = default);
+}

src/Modules/Hello/Mccn.Modules.Hello.Application/Mccn.Modules.Hello.Application.csproj

@@ -2,6 +2,7 @@
 
     <ItemGroup>
         <ProjectReference Include="..\..\..\Common\Mccn.Common.Application\Mccn.Common.Application.csproj"/>
+        <ProjectReference Include="..\..\Users\Mccn.Modules.Users.IntegrationEvents\Mccn.Modules.Users.IntegrationEvents.csproj"/>
     </ItemGroup>
 
     <PropertyGroup>

src/Modules/Hello/Mccn.Modules.Hello.Application/WelcomedUsers/GetWelcomedUsersQuery.cs

@@ -0,0 +1,5 @@
+using Mccn.Common.Application.Abstractions;
+
+namespace Mccn.Modules.Hello.Application.WelcomedUsers;
+
+public sealed record GetWelcomedUsersQuery : IQuery<IReadOnlyList<WelcomedUserResponse>>;

src/Modules/Hello/Mccn.Modules.Hello.Application/WelcomedUsers/GetWelcomedUsersQueryHandler.cs

@@ -0,0 +1,16 @@
+using Mccn.Common.Application.Abstractions;
+using Mccn.Common.Domain.Abstractions;
+
+namespace Mccn.Modules.Hello.Application.WelcomedUsers;
+
+internal sealed class GetWelcomedUsersQueryHandler(IWelcomedUserRepository repository)
+    : IQueryHandler<GetWelcomedUsersQuery, IReadOnlyList<WelcomedUserResponse>>
+{
+    public async Task<Result<IReadOnlyList<WelcomedUserResponse>>> Handle(
+        GetWelcomedUsersQuery request,
+        CancellationToken cancellationToken)
+    {
+        IReadOnlyList<WelcomedUserResponse> users = await repository.GetAllAsync(cancellationToken);
+        return Result.Success(users);
+    }
+}

src/Modules/Hello/Mccn.Modules.Hello.Application/WelcomedUsers/IWelcomedUserRepository.cs

@@ -0,0 +1,14 @@
+namespace Mccn.Modules.Hello.Application.WelcomedUsers;
+
+public interface IWelcomedUserRepository
+{
+    Task AddAsync(
+        Guid userId,
+        string email,
+        string firstName,
+        string lastName,
+        DateTime welcomedAt,
+        CancellationToken cancellationToken = default);
+
+    Task<IReadOnlyList<WelcomedUserResponse>> GetAllAsync(CancellationToken cancellationToken = default);
+}

src/Modules/Hello/Mccn.Modules.Hello.Application/WelcomedUsers/UserRegisteredIntegrationEventHandler.cs

@@ -0,0 +1,26 @@
+using Mccn.Common.Application.EventBus;
+using Mccn.Modules.Hello.Application.Abstractions;
+using Mccn.Modules.Users.IntegrationEvents;
+
+namespace Mccn.Modules.Hello.Application.WelcomedUsers;
+
+public sealed class UserRegisteredIntegrationEventHandler(
+    IWelcomedUserRepository repository,
+    IUnitOfWork unitOfWork)
+    : IntegrationEventHandler<UserRegisteredIntegrationEvent>
+{
+    public override async Task Handle(
+        UserRegisteredIntegrationEvent integrationEvent,
+        CancellationToken cancellationToken)
+    {
+        await repository.AddAsync(
+            integrationEvent.UserId,
+            integrationEvent.Email,
+            integrationEvent.FirstName,
+            integrationEvent.LastName,
+            integrationEvent.OccurredOnUtc,
+            cancellationToken);
+
+        await unitOfWork.SaveChangesAsync(cancellationToken);
+    }
+}

src/Modules/Hello/Mccn.Modules.Hello.Application/WelcomedUsers/WelcomedUserResponse.cs

@@ -0,0 +1,8 @@
+namespace Mccn.Modules.Hello.Application.WelcomedUsers;
+
+public sealed record WelcomedUserResponse(
+    Guid UserId,
+    string Email,
+    string FirstName,
+    string LastName,
+    DateTime WelcomedAt);

src/Modules/Hello/Mccn.Modules.Hello.Infrastructure/Database/Configurations/InboxMessageConfiguration.cs

@@ -0,0 +1,16 @@
+using Mccn.Common.Infrastructure.Inbox;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace Mccn.Modules.Hello.Infrastructure.Database.Configurations;
+
+internal sealed class InboxMessageConfiguration : IEntityTypeConfiguration<InboxMessage>
+{
+    public void Configure(EntityTypeBuilder<InboxMessage> builder)
+    {
+        builder.ToTable("inbox_messages");
+        builder.HasKey(i => i.Id);
+        builder.Property(i => i.Type).IsRequired();
+        builder.Property(i => i.Content).IsRequired();
+    }
+}

src/Modules/Hello/Mccn.Modules.Hello.Infrastructure/Database/Configurations/InboxMessageConsumerConfiguration.cs

@@ -0,0 +1,14 @@
+using Mccn.Common.Infrastructure.Inbox;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace Mccn.Modules.Hello.Infrastructure.Database.Configurations;
+
+internal sealed class InboxMessageConsumerConfiguration : IEntityTypeConfiguration<InboxMessageConsumer>
+{
+    public void Configure(EntityTypeBuilder<InboxMessageConsumer> builder)
+    {
+        builder.ToTable("inbox_message_consumers");
+        builder.HasKey(c => new { c.InboxMessageId, c.Name });
+    }
+}

src/Modules/Hello/Mccn.Modules.Hello.Infrastructure/Database/Configurations/WelcomedUserConfiguration.cs

@@ -0,0 +1,17 @@
+using Mccn.Modules.Hello.Infrastructure.Database.Models;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace Mccn.Modules.Hello.Infrastructure.Database.Configurations;
+
+internal sealed class WelcomedUserConfiguration : IEntityTypeConfiguration<WelcomedUser>
+{
+    public void Configure(EntityTypeBuilder<WelcomedUser> builder)
+    {
+        builder.ToTable("welcomed_users");
+        builder.HasKey(w => w.Id);
+        builder.Property(w => w.Email).IsRequired();
+        builder.Property(w => w.FirstName).IsRequired();
+        builder.Property(w => w.LastName).IsRequired();
+    }
+}

src/Modules/Hello/Mccn.Modules.Hello.Infrastructure/Database/HelloDbContext.cs

@@ -0,0 +1,23 @@
+using Mccn.Common.Infrastructure.Inbox;
+using Mccn.Modules.Hello.Infrastructure.Database.Models;
+using Microsoft.EntityFrameworkCore;
+
+namespace Mccn.Modules.Hello.Infrastructure.Database;
+
+public sealed class HelloDbContext : DbContext
+{
+    public HelloDbContext(DbContextOptions<HelloDbContext> options)
+        : base(options)
+    {
+    }
+
+    public DbSet<WelcomedUser> WelcomedUsers { get; set; }
+    public DbSet<InboxMessage> InboxMessages { get; set; }
+    public DbSet<InboxMessageConsumer> InboxMessageConsumers { get; set; }
+
+    protected override void OnModelCreating(ModelBuilder modelBuilder)
+    {
+        modelBuilder.HasDefaultSchema(Schemas.Hello);
+        modelBuilder.ApplyConfigurationsFromAssembly(typeof(HelloDbContext).Assembly);
+    }
+}

src/Modules/Hello/Mccn.Modules.Hello.Infrastructure/Database/Models/WelcomedUser.cs

@@ -0,0 +1,11 @@
+namespace Mccn.Modules.Hello.Infrastructure.Database.Models;
+
+public sealed class WelcomedUser
+{
+    public Guid Id { get; init; }
+    public Guid UserId { get; init; }
+    public string Email { get; init; } = string.Empty;
+    public string FirstName { get; init; } = string.Empty;
+    public string LastName { get; init; } = string.Empty;
+    public DateTime WelcomedAt { get; init; }
+}

src/Modules/Hello/Mccn.Modules.Hello.Infrastructure/Database/Schemas.cs

@@ -0,0 +1,6 @@
+namespace Mccn.Modules.Hello.Infrastructure.Database;
+
+internal static class Schemas
+{
+    internal const string Hello = "hello";
+}

src/Modules/Hello/Mccn.Modules.Hello.Infrastructure/DependencyInjection.cs

@@ -1,16 +1,54 @@
+using MassTransit;
+using Mccn.Common.Application.EventBus;
+using Mccn.Modules.Hello.Application.Abstractions;
+using Mccn.Modules.Hello.Application.WelcomedUsers;
+using Mccn.Modules.Hello.Infrastructure.Database;
+using Mccn.Modules.Hello.Infrastructure.Inbox;
+using Mccn.Modules.Hello.Infrastructure.WelcomedUsers;
+using Mccn.Modules.Users.IntegrationEvents;
+using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
+using Quartz;
 
 namespace Mccn.Modules.Hello.Infrastructure;
 
 public static class DependencyInjection
 {
+    public static void ConfigureConsumers(IRegistrationConfigurator configurator)
+    {
+        configurator.AddConsumer<IntegrationEventConsumer<UserRegisteredIntegrationEvent>>();
+    }
+
     public static IServiceCollection AddHelloModule(
         this IServiceCollection services,
         IConfiguration configuration)
     {
-        // Hello module has no database/infrastructure dependencies.
+        services.AddDbContext<HelloDbContext>(options =>
-        // This is where you'd add them when the module grows.
+        {
+            options.UseNpgsql(
+                    configuration.GetConnectionString("Database"),
+                    o => o.MigrationsHistoryTable("__ef_migrations_history", Schemas.Hello))
+                .UseSnakeCaseNamingConvention();
+        });
+
+        services.AddScoped<IWelcomedUserRepository, WelcomedUserRepository>();
+        services.AddScoped<IUnitOfWork, UnitOfWork>();
+
+        // Register integration event handlers so ProcessInboxJob can resolve them.
+        services.AddScoped<
+            IIntegrationEventHandler<UserRegisteredIntegrationEvent>,
+            UserRegisteredIntegrationEventHandler>();
+
+        services.AddQuartz(q =>
+        {
+            var jobKey = new JobKey(nameof(ProcessInboxJob));
+            q.AddJob<ProcessInboxJob>(opts => opts.WithIdentity(jobKey));
+            q.AddTrigger(opts => opts
+                .ForJob(jobKey)
+                .WithSimpleSchedule(s => s.WithIntervalInSeconds(10).RepeatForever()));
+        });
+
         return services;
     }
 }

src/Modules/Hello/Mccn.Modules.Hello.Infrastructure/Inbox/IntegrationEventConsumer.cs

@@ -0,0 +1,28 @@
+using System.Text.Json;
+using MassTransit;
+using Mccn.Common.Application.EventBus;
+using Mccn.Common.Infrastructure.Inbox;
+using Mccn.Modules.Hello.Infrastructure.Database;
+
+namespace Mccn.Modules.Hello.Infrastructure.Inbox;
+
+internal sealed class IntegrationEventConsumer<TIntegrationEvent>(HelloDbContext dbContext)
+    : IConsumer<TIntegrationEvent>
+    where TIntegrationEvent : class, IIntegrationEvent
+{
+    public async Task Consume(ConsumeContext<TIntegrationEvent> context)
+    {
+        TIntegrationEvent integrationEvent = context.Message;
+
+        var inboxMessage = new InboxMessage
+        {
+            Id = integrationEvent.Id,
+            Type = integrationEvent.GetType().Name,
+            Content = JsonSerializer.Serialize(integrationEvent, integrationEvent.GetType()),
+            OccurredOnUtc = integrationEvent.OccurredOnUtc
+        };
+
+        await dbContext.InboxMessages.AddAsync(inboxMessage, context.CancellationToken);
+        await dbContext.SaveChangesAsync(context.CancellationToken);
+    }
+}

src/Modules/Hello/Mccn.Modules.Hello.Infrastructure/Inbox/ProcessInboxJob.cs

@@ -0,0 +1,103 @@
+using System.Reflection;
+using System.Text.Json;
+using Mccn.Common.Application.EventBus;
+using Mccn.Common.Infrastructure.Inbox;
+using Mccn.Modules.Hello.Application.WelcomedUsers;
+using Mccn.Modules.Hello.Infrastructure.Database;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
+using Quartz;
+
+namespace Mccn.Modules.Hello.Infrastructure.Inbox;
+
+[DisallowConcurrentExecution]
+internal sealed class ProcessInboxJob(
+    HelloDbContext dbContext,
+    IServiceScopeFactory serviceScopeFactory,
+    ILogger<ProcessInboxJob> logger) : IJob
+{
+    // Scan the Application assembly for integration event handler types.
+    private static readonly Assembly ApplicationAssembly =
+        typeof(UserRegisteredIntegrationEventHandler).Assembly;
+
+    public async Task Execute(IJobExecutionContext context)
+    {
+        List<InboxMessage> messages = await dbContext.InboxMessages
+            .Where(m => m.ProcessedOnUtc == null)
+            .OrderBy(m => m.OccurredOnUtc)
+            .Take(20)
+            .ToListAsync(context.CancellationToken);
+
+        foreach (InboxMessage message in messages)
+        {
+            try
+            {
+                Type? eventType = ApplicationAssembly.GetReferencedAssemblies()
+                    .Select(Assembly.Load)
+                    .Concat([ApplicationAssembly])
+                    .SelectMany(a => a.GetTypes())
+                    .FirstOrDefault(t => t.Name == message.Type);
+
+                if (eventType is null)
+                {
+                    logger.LogWarning("Could not find integration event type {Type}", message.Type);
+                    message.ProcessedOnUtc = DateTime.UtcNow;
+                    message.Error = $"Unknown integration event type: {message.Type}";
+                    continue;
+                }
+
+                IIntegrationEvent? integrationEvent =
+                    (IIntegrationEvent?)JsonSerializer.Deserialize(message.Content, eventType);
+
+                if (integrationEvent is null)
+                {
+                    message.ProcessedOnUtc = DateTime.UtcNow;
+                    message.Error = "Failed to deserialize integration event.";
+                    continue;
+                }
+
+                using IServiceScope scope = serviceScopeFactory.CreateScope();
+
+                Type handlerInterfaceType = typeof(IIntegrationEventHandler<>).MakeGenericType(eventType);
+
+                IEnumerable<IIntegrationEventHandler> handlers = scope.ServiceProvider
+                    .GetServices(handlerInterfaceType)
+                    .Cast<IIntegrationEventHandler>();
+
+                foreach (IIntegrationEventHandler handler in handlers)
+                {
+                    string consumerName = handler.GetType().Name;
+
+                    bool alreadyProcessed = await dbContext.InboxMessageConsumers
+                        .AnyAsync(
+                            c => c.InboxMessageId == message.Id && c.Name == consumerName,
+                            context.CancellationToken);
+
+                    if (alreadyProcessed)
+                        continue;
+
+                    await handler.Handle(integrationEvent, context.CancellationToken);
+
+                    dbContext.InboxMessageConsumers.Add(new InboxMessageConsumer
+                    {
+                        InboxMessageId = message.Id,
+                        Name = consumerName
+                    });
+
+                    await dbContext.SaveChangesAsync(context.CancellationToken);
+                }
+
+                message.ProcessedOnUtc = DateTime.UtcNow;
+            }
+            catch (Exception ex)
+            {
+                logger.LogError(ex, "Error processing inbox message {MessageId}", message.Id);
+                message.Error = ex.Message;
+                message.ProcessedOnUtc = DateTime.UtcNow;
+            }
+        }
+
+        await dbContext.SaveChangesAsync(context.CancellationToken);
+    }
+}

src/Modules/Hello/Mccn.Modules.Hello.Infrastructure/Mccn.Modules.Hello.Infrastructure.csproj

@@ -5,6 +5,12 @@
         <ProjectReference Include="..\..\..\Common\Mccn.Common.Infrastructure\Mccn.Common.Infrastructure.csproj"/>
     </ItemGroup>
 
+    <ItemGroup>
+        <PackageReference Include="EFCore.NamingConventions" Version="10.0.1"/>
+        <PackageReference Include="Microsoft.EntityFrameworkCore" Version="10.0.4"/>
+        <PackageReference Include="Npgsql.EntityFrameworkCore.PostgreSQL" Version="10.0.1"/>
+    </ItemGroup>
+
     <PropertyGroup>
         <TargetFramework>net10.0</TargetFramework>
         <ImplicitUsings>enable</ImplicitUsings>

src/Modules/Hello/Mccn.Modules.Hello.Infrastructure/Migrations/20260315153129_InitialCreate.Designer.cs

@@ -0,0 +1,118 @@
+// <auto-generated />
+using System;
+using Mccn.Modules.Hello.Infrastructure.Database;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
+using Npgsql.EntityFrameworkCore.PostgreSQL.Metadata;
+
+#nullable disable
+
+namespace Mccn.Modules.Hello.Infrastructure.Migrations
+{
+    [DbContext(typeof(HelloDbContext))]
+    [Migration("20260315153129_InitialCreate")]
+    partial class InitialCreate
+    {
+        /// <inheritdoc />
+        protected override void BuildTargetModel(ModelBuilder modelBuilder)
+        {
+#pragma warning disable 612, 618
+            modelBuilder
+                .HasDefaultSchema("hello")
+                .HasAnnotation("ProductVersion", "10.0.4")
+                .HasAnnotation("Relational:MaxIdentifierLength", 63);
+
+            NpgsqlModelBuilderExtensions.UseIdentityByDefaultColumns(modelBuilder);
+
+            modelBuilder.Entity("Mccn.Common.Infrastructure.Inbox.InboxMessage", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid")
+                        .HasColumnName("id");
+
+                    b.Property<string>("Content")
+                        .IsRequired()
+                        .HasColumnType("text")
+                        .HasColumnName("content");
+
+                    b.Property<string>("Error")
+                        .HasColumnType("text")
+                        .HasColumnName("error");
+
+                    b.Property<DateTime>("OccurredOnUtc")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("occurred_on_utc");
+
+                    b.Property<DateTime?>("ProcessedOnUtc")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("processed_on_utc");
+
+                    b.Property<string>("Type")
+                        .IsRequired()
+                        .HasColumnType("text")
+                        .HasColumnName("type");
+
+                    b.HasKey("Id")
+                        .HasName("pk_inbox_messages");
+
+                    b.ToTable("inbox_messages", "hello");
+                });
+
+            modelBuilder.Entity("Mccn.Common.Infrastructure.Inbox.InboxMessageConsumer", b =>
+                {
+                    b.Property<Guid>("InboxMessageId")
+                        .HasColumnType("uuid")
+                        .HasColumnName("inbox_message_id");
+
+                    b.Property<string>("Name")
+                        .HasColumnType("text")
+                        .HasColumnName("name");
+
+                    b.HasKey("InboxMessageId", "Name")
+                        .HasName("pk_inbox_message_consumers");
+
+                    b.ToTable("inbox_message_consumers", "hello");
+                });
+
+            modelBuilder.Entity("Mccn.Modules.Hello.Infrastructure.Database.Models.WelcomedUser", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid")
+                        .HasColumnName("id");
+
+                    b.Property<string>("Email")
+                        .IsRequired()
+                        .HasColumnType("text")
+                        .HasColumnName("email");
+
+                    b.Property<string>("FirstName")
+                        .IsRequired()
+                        .HasColumnType("text")
+                        .HasColumnName("first_name");
+
+                    b.Property<string>("LastName")
+                        .IsRequired()
+                        .HasColumnType("text")
+                        .HasColumnName("last_name");
+
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("uuid")
+                        .HasColumnName("user_id");
+
+                    b.Property<DateTime>("WelcomedAt")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("welcomed_at");
+
+                    b.HasKey("Id")
+                        .HasName("pk_welcomed_users");
+
+                    b.ToTable("welcomed_users", "hello");
+                });
+#pragma warning restore 612, 618
+        }
+    }
+}

src/Modules/Hello/Mccn.Modules.Hello.Infrastructure/Migrations/20260315153129_InitialCreate.cs

@@ -0,0 +1,81 @@
+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace Mccn.Modules.Hello.Infrastructure.Migrations
+{
+    /// <inheritdoc />
+    public partial class InitialCreate : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.EnsureSchema(
+                name: "hello");
+
+            migrationBuilder.CreateTable(
+                name: "inbox_message_consumers",
+                schema: "hello",
+                columns: table => new
+                {
+                    inbox_message_id = table.Column<Guid>(type: "uuid", nullable: false),
+                    name = table.Column<string>(type: "text", nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("pk_inbox_message_consumers", x => new { x.inbox_message_id, x.name });
+                });
+
+            migrationBuilder.CreateTable(
+                name: "inbox_messages",
+                schema: "hello",
+                columns: table => new
+                {
+                    id = table.Column<Guid>(type: "uuid", nullable: false),
+                    type = table.Column<string>(type: "text", nullable: false),
+                    content = table.Column<string>(type: "text", nullable: false),
+                    occurred_on_utc = table.Column<DateTime>(type: "timestamp with time zone", nullable: false),
+                    processed_on_utc = table.Column<DateTime>(type: "timestamp with time zone", nullable: true),
+                    error = table.Column<string>(type: "text", nullable: true)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("pk_inbox_messages", x => x.id);
+                });
+
+            migrationBuilder.CreateTable(
+                name: "welcomed_users",
+                schema: "hello",
+                columns: table => new
+                {
+                    id = table.Column<Guid>(type: "uuid", nullable: false),
+                    user_id = table.Column<Guid>(type: "uuid", nullable: false),
+                    email = table.Column<string>(type: "text", nullable: false),
+                    first_name = table.Column<string>(type: "text", nullable: false),
+                    last_name = table.Column<string>(type: "text", nullable: false),
+                    welcomed_at = table.Column<DateTime>(type: "timestamp with time zone", nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("pk_welcomed_users", x => x.id);
+                });
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropTable(
+                name: "inbox_message_consumers",
+                schema: "hello");
+
+            migrationBuilder.DropTable(
+                name: "inbox_messages",
+                schema: "hello");
+
+            migrationBuilder.DropTable(
+                name: "welcomed_users",
+                schema: "hello");
+        }
+    }
+}

src/Modules/Hello/Mccn.Modules.Hello.Infrastructure/Migrations/HelloDbContextModelSnapshot.cs

@@ -0,0 +1,115 @@
+// <auto-generated />
+using System;
+using Mccn.Modules.Hello.Infrastructure.Database;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
+using Npgsql.EntityFrameworkCore.PostgreSQL.Metadata;
+
+#nullable disable
+
+namespace Mccn.Modules.Hello.Infrastructure.Migrations
+{
+    [DbContext(typeof(HelloDbContext))]
+    partial class HelloDbContextModelSnapshot : ModelSnapshot
+    {
+        protected override void BuildModel(ModelBuilder modelBuilder)
+        {
+#pragma warning disable 612, 618
+            modelBuilder
+                .HasDefaultSchema("hello")
+                .HasAnnotation("ProductVersion", "10.0.4")
+                .HasAnnotation("Relational:MaxIdentifierLength", 63);
+
+            NpgsqlModelBuilderExtensions.UseIdentityByDefaultColumns(modelBuilder);
+
+            modelBuilder.Entity("Mccn.Common.Infrastructure.Inbox.InboxMessage", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid")
+                        .HasColumnName("id");
+
+                    b.Property<string>("Content")
+                        .IsRequired()
+                        .HasColumnType("text")
+                        .HasColumnName("content");
+
+                    b.Property<string>("Error")
+                        .HasColumnType("text")
+                        .HasColumnName("error");
+
+                    b.Property<DateTime>("OccurredOnUtc")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("occurred_on_utc");
+
+                    b.Property<DateTime?>("ProcessedOnUtc")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("processed_on_utc");
+
+                    b.Property<string>("Type")
+                        .IsRequired()
+                        .HasColumnType("text")
+                        .HasColumnName("type");
+
+                    b.HasKey("Id")
+                        .HasName("pk_inbox_messages");
+
+                    b.ToTable("inbox_messages", "hello");
+                });
+
+            modelBuilder.Entity("Mccn.Common.Infrastructure.Inbox.InboxMessageConsumer", b =>
+                {
+                    b.Property<Guid>("InboxMessageId")
+                        .HasColumnType("uuid")
+                        .HasColumnName("inbox_message_id");
+
+                    b.Property<string>("Name")
+                        .HasColumnType("text")
+                        .HasColumnName("name");
+
+                    b.HasKey("InboxMessageId", "Name")
+                        .HasName("pk_inbox_message_consumers");
+
+                    b.ToTable("inbox_message_consumers", "hello");
+                });
+
+            modelBuilder.Entity("Mccn.Modules.Hello.Infrastructure.Database.Models.WelcomedUser", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid")
+                        .HasColumnName("id");
+
+                    b.Property<string>("Email")
+                        .IsRequired()
+                        .HasColumnType("text")
+                        .HasColumnName("email");
+
+                    b.Property<string>("FirstName")
+                        .IsRequired()
+                        .HasColumnType("text")
+                        .HasColumnName("first_name");
+
+                    b.Property<string>("LastName")
+                        .IsRequired()
+                        .HasColumnType("text")
+                        .HasColumnName("last_name");
+
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("uuid")
+                        .HasColumnName("user_id");
+
+                    b.Property<DateTime>("WelcomedAt")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("welcomed_at");
+
+                    b.HasKey("Id")
+                        .HasName("pk_welcomed_users");
+
+                    b.ToTable("welcomed_users", "hello");
+                });
+#pragma warning restore 612, 618
+        }
+    }
+}

src/Modules/Hello/Mccn.Modules.Hello.Infrastructure/WelcomedUsers/UnitOfWork.cs

@@ -0,0 +1,10 @@
+using Mccn.Modules.Hello.Application.Abstractions;
+using Mccn.Modules.Hello.Infrastructure.Database;
+
+namespace Mccn.Modules.Hello.Infrastructure.WelcomedUsers;
+
+internal sealed class UnitOfWork(HelloDbContext dbContext) : IUnitOfWork
+{
+    public async Task SaveChangesAsync(CancellationToken cancellationToken = default) =>
+        await dbContext.SaveChangesAsync(cancellationToken);
+}

src/Modules/Hello/Mccn.Modules.Hello.Infrastructure/WelcomedUsers/WelcomedUserRepository.cs

@@ -0,0 +1,44 @@
+using Mccn.Modules.Hello.Application.WelcomedUsers;
+using Mccn.Modules.Hello.Infrastructure.Database;
+using Mccn.Modules.Hello.Infrastructure.Database.Models;
+using Microsoft.EntityFrameworkCore;
+
+namespace Mccn.Modules.Hello.Infrastructure.WelcomedUsers;
+
+internal sealed class WelcomedUserRepository(HelloDbContext dbContext) : IWelcomedUserRepository
+{
+    public async Task AddAsync(
+        Guid userId,
+        string email,
+        string firstName,
+        string lastName,
+        DateTime welcomedAt,
+        CancellationToken cancellationToken = default)
+    {
+        var welcomedUser = new WelcomedUser
+        {
+            Id = Guid.NewGuid(),
+            UserId = userId,
+            Email = email,
+            FirstName = firstName,
+            LastName = lastName,
+            WelcomedAt = welcomedAt
+        };
+
+        await dbContext.WelcomedUsers.AddAsync(welcomedUser, cancellationToken);
+    }
+
+    public async Task<IReadOnlyList<WelcomedUserResponse>> GetAllAsync(
+        CancellationToken cancellationToken = default)
+    {
+        return await dbContext.WelcomedUsers
+            .OrderByDescending(w => w.WelcomedAt)
+            .Select(w => new WelcomedUserResponse(
+                w.UserId,
+                w.Email,
+                w.FirstName,
+                w.LastName,
+                w.WelcomedAt))
+            .ToListAsync(cancellationToken);
+    }
+}

src/Modules/Hello/Mccn.Modules.Hello.Presentation/Hello/GetWelcomedUsers.cs

@@ -0,0 +1,25 @@
+using Mccn.Common.Domain.Abstractions;
+using Mccn.Common.Presentation.Endpoints;
+using Mccn.Modules.Hello.Application.WelcomedUsers;
+using MediatR;
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Routing;
+
+namespace Mccn.Modules.Hello.Presentation.Hello;
+
+internal sealed class GetWelcomedUsers : IEndpoint
+{
+    public void MapEndpoint(IEndpointRouteBuilder app)
+    {
+        app.MapGet("hello/welcomed-users", async (ISender sender) =>
+        {
+            Result<IReadOnlyList<WelcomedUserResponse>> result =
+                await sender.Send(new GetWelcomedUsersQuery());
+
+            return Results.Ok(result.Value);
+        })
+        .WithTags("Hello")
+        .AllowAnonymous();
+    }
+}

src/Modules/Users/Mccn.Modules.Users.Application/Mccn.Modules.Users.Application.csproj

@@ -2,6 +2,7 @@
 
     <ItemGroup>
         <ProjectReference Include="..\Mccn.Modules.Users.Domain\Mccn.Modules.Users.Domain.csproj"/>
+        <ProjectReference Include="..\Mccn.Modules.Users.IntegrationEvents\Mccn.Modules.Users.IntegrationEvents.csproj"/>
         <ProjectReference Include="..\..\..\Common\Mccn.Common.Application\Mccn.Common.Application.csproj"/>
     </ItemGroup>
 

src/Modules/Users/Mccn.Modules.Users.Application/Users/Register/UserRegisteredDomainEventHandler.cs

@@ -0,0 +1,22 @@
+using Mccn.Common.Application.EventBus;
+using Mccn.Modules.Users.Domain.Users;
+using Mccn.Modules.Users.IntegrationEvents;
+
+namespace Mccn.Modules.Users.Application.Users.Register;
+
+internal sealed class UserRegisteredDomainEventHandler(IEventBus eventBus)
+    : DomainEventHandler<UserRegisteredDomainEvent>
+{
+    public override async Task Handle(
+        UserRegisteredDomainEvent domainEvent,
+        CancellationToken cancellationToken)
+    {
+        await eventBus.PublishAsync(new UserRegisteredIntegrationEvent(
+            domainEvent.Id,
+            domainEvent.OccurredOnUtc,
+            domainEvent.UserId,
+            domainEvent.Email,
+            domainEvent.FirstName,
+            domainEvent.LastName), cancellationToken);
+    }
+}

src/Modules/Users/Mccn.Modules.Users.Domain/Users/User.cs

@@ -20,7 +20,7 @@ public sealed class User : Entity
         string lastName,
         string identityId)
     {
-        return new User
+        var user = new User
         {
             Id = id,
             Email = email,
@@ -28,5 +28,15 @@ public sealed class User : Entity
             LastName = lastName,
             IdentityId = identityId
         };
+
+        user.RaiseDomainEvent(new UserRegisteredDomainEvent(
+            Guid.NewGuid(),
+            DateTime.UtcNow,
+            user.Id,
+            user.Email,
+            user.FirstName,
+            user.LastName));
+
+        return user;
     }
 }

src/Modules/Users/Mccn.Modules.Users.Domain/Users/UserRegisteredDomainEvent.cs

@@ -0,0 +1,11 @@
+using Mccn.Common.Domain.Abstractions;
+
+namespace Mccn.Modules.Users.Domain.Users;
+
+public sealed record UserRegisteredDomainEvent(
+    Guid Id,
+    DateTime OccurredOnUtc,
+    Guid UserId,
+    string Email,
+    string FirstName,
+    string LastName) : DomainEvent(Id, OccurredOnUtc);

src/Modules/Users/Mccn.Modules.Users.Infrastructure/Database/Configurations/OutboxMessageConfiguration.cs

@@ -0,0 +1,16 @@
+using Mccn.Common.Infrastructure.Outbox;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace Mccn.Modules.Users.Infrastructure.Database.Configurations;
+
+internal sealed class OutboxMessageConfiguration : IEntityTypeConfiguration<OutboxMessage>
+{
+    public void Configure(EntityTypeBuilder<OutboxMessage> builder)
+    {
+        builder.ToTable("outbox_messages");
+        builder.HasKey(o => o.Id);
+        builder.Property(o => o.Type).IsRequired();
+        builder.Property(o => o.Content).IsRequired();
+    }
+}

src/Modules/Users/Mccn.Modules.Users.Infrastructure/Database/Migrations/20260315153115_AddOutboxMessages.Designer.cs

@@ -0,0 +1,111 @@
+// <auto-generated />
+using System;
+using Mccn.Modules.Users.Infrastructure.Database;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
+using Npgsql.EntityFrameworkCore.PostgreSQL.Metadata;
+
+#nullable disable
+
+namespace Mccn.Modules.Users.Infrastructure.Database.Migrations
+{
+    [DbContext(typeof(UsersDbContext))]
+    [Migration("20260315153115_AddOutboxMessages")]
+    partial class AddOutboxMessages
+    {
+        /// <inheritdoc />
+        protected override void BuildTargetModel(ModelBuilder modelBuilder)
+        {
+#pragma warning disable 612, 618
+            modelBuilder
+                .HasDefaultSchema("users")
+                .HasAnnotation("ProductVersion", "10.0.4")
+                .HasAnnotation("Relational:MaxIdentifierLength", 63);
+
+            NpgsqlModelBuilderExtensions.UseIdentityByDefaultColumns(modelBuilder);
+
+            modelBuilder.Entity("Mccn.Common.Infrastructure.Outbox.OutboxMessage", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid")
+                        .HasColumnName("id");
+
+                    b.Property<string>("Content")
+                        .IsRequired()
+                        .HasColumnType("text")
+                        .HasColumnName("content");
+
+                    b.Property<string>("Error")
+                        .HasColumnType("text")
+                        .HasColumnName("error");
+
+                    b.Property<DateTime>("OccurredOnUtc")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("occurred_on_utc");
+
+                    b.Property<DateTime?>("ProcessedOnUtc")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("processed_on_utc");
+
+                    b.Property<string>("Type")
+                        .IsRequired()
+                        .HasColumnType("text")
+                        .HasColumnName("type");
+
+                    b.HasKey("Id")
+                        .HasName("pk_outbox_messages");
+
+                    b.ToTable("outbox_messages", "users");
+                });
+
+            modelBuilder.Entity("Mccn.Modules.Users.Domain.Users.User", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid")
+                        .HasColumnName("id");
+
+                    b.Property<string>("Email")
+                        .IsRequired()
+                        .HasMaxLength(300)
+                        .HasColumnType("character varying(300)")
+                        .HasColumnName("email");
+
+                    b.Property<string>("FirstName")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("character varying(100)")
+                        .HasColumnName("first_name");
+
+                    b.Property<string>("IdentityId")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("character varying(100)")
+                        .HasColumnName("identity_id");
+
+                    b.Property<string>("LastName")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("character varying(100)")
+                        .HasColumnName("last_name");
+
+                    b.HasKey("Id")
+                        .HasName("pk_users");
+
+                    b.HasIndex("Email")
+                        .IsUnique()
+                        .HasDatabaseName("ix_users_email");
+
+                    b.HasIndex("IdentityId")
+                        .IsUnique()
+                        .HasDatabaseName("ix_users_identity_id");
+
+                    b.ToTable("users", "users");
+                });
+#pragma warning restore 612, 618
+        }
+    }
+}

src/Modules/Users/Mccn.Modules.Users.Infrastructure/Database/Migrations/20260315153115_AddOutboxMessages.cs

@@ -0,0 +1,40 @@
+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace Mccn.Modules.Users.Infrastructure.Database.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddOutboxMessages : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.CreateTable(
+                name: "outbox_messages",
+                schema: "users",
+                columns: table => new
+                {
+                    id = table.Column<Guid>(type: "uuid", nullable: false),
+                    type = table.Column<string>(type: "text", nullable: false),
+                    content = table.Column<string>(type: "text", nullable: false),
+                    occurred_on_utc = table.Column<DateTime>(type: "timestamp with time zone", nullable: false),
+                    processed_on_utc = table.Column<DateTime>(type: "timestamp with time zone", nullable: true),
+                    error = table.Column<string>(type: "text", nullable: true)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("pk_outbox_messages", x => x.id);
+                });
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropTable(
+                name: "outbox_messages",
+                schema: "users");
+        }
+    }
+}

src/Modules/Users/Mccn.Modules.Users.Infrastructure/Database/Migrations/UsersDbContextModelSnapshot.cs

@@ -18,11 +18,46 @@ namespace Mccn.Modules.Users.Infrastructure.Database.Migrations
 #pragma warning disable 612, 618
             modelBuilder
                 .HasDefaultSchema("users")
-                .HasAnnotation("ProductVersion", "10.0.5")
+                .HasAnnotation("ProductVersion", "10.0.4")
                 .HasAnnotation("Relational:MaxIdentifierLength", 63);
 
             NpgsqlModelBuilderExtensions.UseIdentityByDefaultColumns(modelBuilder);
 
+            modelBuilder.Entity("Mccn.Common.Infrastructure.Outbox.OutboxMessage", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid")
+                        .HasColumnName("id");
+
+                    b.Property<string>("Content")
+                        .IsRequired()
+                        .HasColumnType("text")
+                        .HasColumnName("content");
+
+                    b.Property<string>("Error")
+                        .HasColumnType("text")
+                        .HasColumnName("error");
+
+                    b.Property<DateTime>("OccurredOnUtc")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("occurred_on_utc");
+
+                    b.Property<DateTime?>("ProcessedOnUtc")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("processed_on_utc");
+
+                    b.Property<string>("Type")
+                        .IsRequired()
+                        .HasColumnType("text")
+                        .HasColumnName("type");
+
+                    b.HasKey("Id")
+                        .HasName("pk_outbox_messages");
+
+                    b.ToTable("outbox_messages", "users");
+                });
+
             modelBuilder.Entity("Mccn.Modules.Users.Domain.Users.User", b =>
                 {
                     b.Property<Guid>("Id")

src/Modules/Users/Mccn.Modules.Users.Infrastructure/Database/UsersDbContext.cs

@@ -1,16 +1,13 @@
+using Mccn.Common.Infrastructure.Outbox;
 using Mccn.Modules.Users.Domain.Users;
 using Microsoft.EntityFrameworkCore;
 
 namespace Mccn.Modules.Users.Infrastructure.Database;
 
-public sealed class UsersDbContext : DbContext
+public sealed class UsersDbContext(DbContextOptions<UsersDbContext> options) : DbContext(options)
 {
-    public UsersDbContext(DbContextOptions<UsersDbContext> options)
-        : base(options)
-    {
-    }
-
     public DbSet<User> Users { get; set; }
+    public DbSet<OutboxMessage> OutboxMessages { get; set; }
 
     protected override void OnModelCreating(ModelBuilder modelBuilder)
     {

src/Modules/Users/Mccn.Modules.Users.Infrastructure/DependencyInjection.cs

@@ -1,26 +1,38 @@
+using MassTransit;
+using Mccn.Common.Infrastructure.Outbox;
 using Mccn.Modules.Users.Application.Abstractions;
 using Mccn.Modules.Users.Domain.Users;
 using Mccn.Modules.Users.Infrastructure.Database;
 using Mccn.Modules.Users.Infrastructure.Keycloak;
+using Mccn.Modules.Users.Infrastructure.Outbox;
 using Mccn.Modules.Users.Infrastructure.Users;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
+using Quartz;
 
 namespace Mccn.Modules.Users.Infrastructure;
 
 public static class DependencyInjection
 {
+    public static void ConfigureConsumers(IRegistrationConfigurator configurator)
+    {
+        // The Users module publishes events but does not consume any.
+    }
+
     public static IServiceCollection AddUsersModule(
         this IServiceCollection services,
         IConfiguration configuration)
     {
-        services.AddDbContext<UsersDbContext>(options =>
+        services.AddSingleton<InsertOutboxMessagesInterceptor>();
+
+        services.AddDbContext<UsersDbContext>((sp, options) =>
         {
             options.UseNpgsql(
                     configuration.GetConnectionString("Database"),
                     o => o.MigrationsHistoryTable("__ef_migrations_history", Schemas.Users))
-                .UseSnakeCaseNamingConvention();
+                .UseSnakeCaseNamingConvention()
+                .AddInterceptors(sp.GetRequiredService<InsertOutboxMessagesInterceptor>());
         });
 
         services.Configure<KeycloakOptions>(
@@ -40,6 +52,15 @@ public static class DependencyInjection
         services.AddScoped<IUserRepository, UserRepository>();
         services.AddScoped<IUnitOfWork, UnitOfWork>();
 
+        services.AddQuartz(q =>
+        {
+            var jobKey = new JobKey(nameof(ProcessOutboxJob));
+            q.AddJob<ProcessOutboxJob>(opts => opts.WithIdentity(jobKey));
+            q.AddTrigger(opts => opts
+                .ForJob(jobKey)
+                .WithSimpleSchedule(s => s.WithIntervalInSeconds(10).RepeatForever()));
+        });
+
         return services;
     }
 }

src/Modules/Users/Mccn.Modules.Users.Infrastructure/Outbox/ProcessOutboxJob.cs

@@ -0,0 +1,78 @@
+using System.Reflection;
+using System.Text.Json;
+using Mccn.Common.Application.EventBus;
+using Mccn.Common.Domain.Abstractions;
+using Mccn.Common.Infrastructure.Outbox;
+using Mccn.Modules.Users.Domain.Users;
+using Mccn.Modules.Users.Infrastructure.Database;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
+using Quartz;
+
+namespace Mccn.Modules.Users.Infrastructure.Outbox;
+
+[DisallowConcurrentExecution]
+internal sealed class ProcessOutboxJob(
+    UsersDbContext dbContext,
+    IServiceScopeFactory serviceScopeFactory,
+    ILogger<ProcessOutboxJob> logger) : IJob
+{
+    private static readonly Assembly DomainAssembly = typeof(User).Assembly;
+
+    public async Task Execute(IJobExecutionContext context)
+    {
+        List<OutboxMessage> messages = await dbContext.OutboxMessages
+            .Where(m => m.ProcessedOnUtc == null)
+            .OrderBy(m => m.OccurredOnUtc)
+            .Take(20)
+            .ToListAsync(context.CancellationToken);
+
+        foreach (OutboxMessage message in messages)
+        {
+            try
+            {
+                Type? eventType = DomainAssembly.GetTypes()
+                    .FirstOrDefault(t => t.Name == message.Type);
+
+                if (eventType is null)
+                {
+                    logger.LogWarning("Could not find domain event type {Type}", message.Type);
+                    message.ProcessedOnUtc = DateTime.UtcNow;
+                    message.Error = $"Unknown domain event type: {message.Type}";
+                    continue;
+                }
+
+                IDomainEvent? domainEvent = (IDomainEvent?)JsonSerializer.Deserialize(message.Content, eventType);
+
+                if (domainEvent is null)
+                {
+                    message.ProcessedOnUtc = DateTime.UtcNow;
+                    message.Error = "Failed to deserialize domain event.";
+                    continue;
+                }
+
+                using IServiceScope scope = serviceScopeFactory.CreateScope();
+
+                Type handlerInterfaceType = typeof(IDomainEventHandler<>).MakeGenericType(eventType);
+
+                IEnumerable<IDomainEventHandler> handlers = scope.ServiceProvider
+                    .GetServices(handlerInterfaceType)
+                    .Cast<IDomainEventHandler>();
+
+                foreach (IDomainEventHandler handler in handlers)
+                    await handler.Handle(domainEvent, context.CancellationToken);
+
+                message.ProcessedOnUtc = DateTime.UtcNow;
+            }
+            catch (Exception ex)
+            {
+                logger.LogError(ex, "Error processing outbox message {MessageId}", message.Id);
+                message.Error = ex.Message;
+                message.ProcessedOnUtc = DateTime.UtcNow;
+            }
+        }
+
+        await dbContext.SaveChangesAsync(context.CancellationToken);
+    }
+}

src/Modules/Users/Mccn.Modules.Users.IntegrationEvents/Mccn.Modules.Users.IntegrationEvents.csproj

@@ -0,0 +1,7 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <ItemGroup>
+        <ProjectReference Include="..\..\..\Common\Mccn.Common.Application\Mccn.Common.Application.csproj"/>
+    </ItemGroup>
+
+</Project>

src/Modules/Users/Mccn.Modules.Users.IntegrationEvents/UserRegisteredIntegrationEvent.cs

@@ -0,0 +1,11 @@
+using Mccn.Common.Application.EventBus;
+
+namespace Mccn.Modules.Users.IntegrationEvents;
+
+public sealed record UserRegisteredIntegrationEvent(
+    Guid Id,
+    DateTime OccurredOnUtc,
+    Guid UserId,
+    string Email,
+    string FirstName,
+    string LastName) : IntegrationEvent(Id, OccurredOnUtc);

test/Mccn.ArchitectureTests/Abstractions/BaseTest.cs

@@ -4,4 +4,23 @@ public abstract class BaseTest
 {
     protected const string UsersNamespace = "Mccn.Modules.Users";
     protected const string HelloNamespace = "Mccn.Modules.Hello";
+
+    // Implementation namespaces checked for cross-module isolation.
+    // *.IntegrationEvents is excluded because it is a public contract assembly
+    // that other modules are explicitly allowed to reference.
+    protected static readonly string[] UsersImplementationNamespaces =
+    [
+        "Mccn.Modules.Users.Domain",
+        "Mccn.Modules.Users.Application",
+        "Mccn.Modules.Users.Infrastructure",
+        "Mccn.Modules.Users.Presentation"
+    ];
+
+    protected static readonly string[] HelloImplementationNamespaces =
+    [
+        "Mccn.Modules.Hello.Domain",
+        "Mccn.Modules.Hello.Application",
+        "Mccn.Modules.Hello.Infrastructure",
+        "Mccn.Modules.Hello.Presentation"
+    ];
 }

test/Mccn.ArchitectureTests/Layers/ModuleTests.cs

@@ -20,12 +20,17 @@ public class ModuleTests : BaseTest
             typeof(DependencyInjection).Assembly
         ];
 
+        // Check each Hello implementation namespace individually.
+        // Hello.IntegrationEvents would be an allowed reference (public contract), but Hello has none.
+        foreach (string ns in HelloImplementationNamespaces)
+        {
             Types.InAssemblies(usersAssemblies)
                 .Should()
-            .NotHaveDependencyOn(HelloNamespace)
+                .NotHaveDependencyOn(ns)
                 .GetResult()
                 .ShouldBeSuccessful();
         }
+    }
 
     [Fact]
     public void HelloModule_ShouldNotHaveDependencyOn_UsersModule()
@@ -37,10 +42,16 @@ public class ModuleTests : BaseTest
             typeof(Modules.Hello.Infrastructure.DependencyInjection).Assembly
         ];
 
+        // Check each Users implementation namespace individually.
+        // Users.IntegrationEvents is explicitly excluded as it is a public contract
+        // that other modules are permitted to reference.
+        foreach (string ns in UsersImplementationNamespaces)
+        {
             Types.InAssemblies(helloAssemblies)
                 .Should()
-            .NotHaveDependencyOn(UsersNamespace)
+                .NotHaveDependencyOn(ns)
                 .GetResult()
                 .ShouldBeSuccessful();
         }
     }
+}