architecture-patterns

Clean Architecture separates your application into independent layers—entities, use cases, interface adapters, and frameworks—isolating business logic from external dependencies. This structure makes your codebase testable, maintainable, and resilient to technology changes.

Hexagonal Architecture (ports and adapters) emphasizes swappable infrastructure components through defined boundaries, while Clean Architecture focuses on layer isolation and inward dependency rules. Both achieve the same goal—decoupling business logic from frameworks—but Hexagonal is more infrastructure-centric.

Use DDD when modeling complex business domains where shared understanding between developers and domain experts is critical. It provides entities, value objects, and aggregates to express business rules explicitly and maintain a cohesive, resilient core.

Apply layered architecture with FastAPI, Pydantic for validation, and repository interfaces to decouple your data layer. Gradually extract bounded contexts, define clear dependencies, and migrate infrastructure concerns away from business logic using ports-and-adapters patterns.

Yes. FastAPI works well with Clean and Hexagonal patterns. Use Pydantic models for domain entities, define repository interfaces with asyncpg for data access, and structure your use cases as separate service layers to progressively improve maintainability without rewriting everything.

Strict layering can create coupling across layers and slow development if not carefully managed. Service layer bloat and database schema dependencies are common pitfalls. Mitigate these by enforcing inward-only dependencies, using aggregates to define boundaries, and keeping infrastructure concerns isolated.