fastapi-hexagonal

To decouple business logic from infrastructure in a FastAPI project, use hexagonal architecture with a domain core, ports for interfaces, and adapters for inbound and outbound I/O. This enforces domain isolation and improves testability.

The best way to structure an asynchronous FastAPI service layer for testing is to implement async-ready service orchestration with explicit protocols and domain isolation, allowing unit and integration tests to run independently of infrastructure adapters.

Yes, you can use hexagonal architecture with FastAPI for domain-driven design by establishing a clearly defined domain core and separating it from infrastructure using ports and adapters across typical use cases.

To handle outbound persistence and messaging in a FastAPI ports and adapters pattern, define explicit outbound ports as interfaces and implement specific adapters for your database and messaging systems, keeping the domain core isolated.

You should not use hexagonal architecture for a Python API if your project is a small prototype or lacks complex domain logic, as the overhead of defining explicit ports, adapters, and an isolated domain core adds unnecessary structural complexity.