EcommerceModularMonolith

E-Commerce Modular Monolith — Critter Stack Conversion

See also: EcommerceMicroservices/ — the same domain split into separate services communicating via RabbitMQ.

Original Project

Repository: aspnetrun/run-aspnetcore-microservices License: MIT

Same domain as EcommerceMicroservices, but collapsed into a single application demonstrating the modular monolith pattern with Wolverine + Marten.

Architecture

One host, one PostgreSQL database, four modules separated by folder and Marten schema:

EcommerceModularMonolith/
  Program.cs                 ← single host, schema-per-module Marten config
  IntegrationEvents.cs       ← shared messages between modules
  Catalog/                   ← Product CRUD
  Basket/                    ← ShoppingCart CRUD, checkout publishes BasketCheckoutEvent
  Ordering/                  ← Order CRUD, handles BasketCheckoutEvent
  Discount/                  ← Coupon CRUD

Module isolation

Each module has its own Marten schema (catalog, basket, ordering, discount) within the same PostgreSQL database. Modules communicate through durable local queues — messages are persisted via the Marten outbox and survive process restarts.

// Durable local queues for inter-module messaging
opts.LocalQueue("basket-checkout").UseDurableInbox();

// Route integration events to local queues
opts.Publish(x =>
{
    x.Message<BasketCheckoutEvent>();
    x.ToLocalQueue("basket-checkout");
});

Microservices vs Modular Monolith

Aspect	EcommerceMicroservices	EcommerceModularMonolith
Deployment	4 separate processes	1 process
Database	4 PostgreSQL databases	1 database, 4 schemas
Transport	RabbitMQ	Durable local queues
Handler code	Identical	Identical
Infrastructure	Docker Compose + RabbitMQ	PostgreSQL only

The handler code is the same in both versions — only Program.cs and the transport configuration differ. This demonstrates Wolverine's transport abstraction: swap local queues for RabbitMQ when you're ready to split into services.

Running

Requires PostgreSQL only (no RabbitMQ needed).

dotnet run

Swagger UI at /swagger.