clean-architecture

To implement Clean Architecture in a Python FastAPI project, separate your code into Domain, Application, Infrastructure, and Presentation layers. Define domain entities, create application use case interactors, and wire ports to adapters using dependency injection for scalable software design.

In hexagonal architecture, ports define the interfaces for domain and application interactions, while adapters are concrete implementations that connect those ports to external technologies. This pattern allows you to easily swap infrastructure technologies without modifying core business logic.

Structure Domain layers by defining pure entities and value objects containing business rules. Structure Application layers by creating interactor objects that orchestrate use cases, ensuring dependencies point inward toward the domain without referencing external infrastructure frameworks.

Yes, you can apply CQRS in a FastAPI layered architecture by explicitly separating write and read models. This involves routing command operations through domain interactors for writes and designing optimized query handlers for read operations within the application layer.

Follow testing conventions that isolate layers by testing domain entities as pure logic, application interactors with mocked ports, and infrastructure adapters with integration tests. This ensures strict separation of concerns across domain, application, and infrastructure layers.

Avoid Clean Architecture for small FastAPI applications or simple CRUD endpoints where the overhead of defining ports, adapters, and multiple layers outweighs the need for strict separation of concerns and long-term architectural scalability.