Clean Architecture

The Clean Architecture (or Hexagonal Architecture) is designed to separate business rules from the infrastructure and UI. This ensures that the core domain logic is independent of external frameworks like Express, Mongoose, or Kafka.

Directory Structure

src/
├── domain/                 # Core business entities
├── usecases/               # Application-specific business rules
├── interfaces/             # Controllers, Routes, GraphQL resolvers (Adapters)
├── infrastructure/         # External tools (DB, Cache, Kafka, Webserver)
└── index.ts                # Application entry point

Layers of Dependency

1. Domain: Contains entities and business logic used across the application. It has zero dependencies on other layers.
2. Use Cases: Defines application-specific actions (e.g., CreateUser, ProcessPayment). It interacts with Domain and defines Repository Interfaces.
3. Interfaces: Bridges the external world (HTTP, Kafka) to Use Cases. For example, a REST controller transforms a request into a call for a Use Case.
4. Infrastructure: Implements database repository interfaces, handles environment configuration, and manages the webserver.

Why choose Clean Architecture?

• Framework Independent: You can change your DB or web framework with minimal effort.
• Testable: Business logic can be tested in isolation without mocks for the database or webserver.
• Maintainable: Clear separation makes it easier for large teams to work on different parts of the system.