clean-ddd-hexagonal

Structure your scalable backend by dividing code into Domain, Application, and Infrastructure layers. Enforce inward-facing dependencies from Infrastructure to Domain, connecting layers via ports and adapters to prevent concern leakage and ensure maintainability.

Hexagonal architecture for API-driven services isolates the Domain and Application core logic from external systems. It uses ports as interfaces and adapters for implementation, allowing easy swapping of infrastructure components and supporting multiple entry points like APIs, CLIs, or events.

Start implementing DDD by defining a minimal aggregate and one use case within your Domain layer. Define ports for external systems, implement infrastructure adapters, then incrementally introduce domain events, read models, and integration events as your domain grows.

Yes, clean architecture works for event-driven systems by defining clear boundaries and supporting events as primary entry points. Ports and adapters isolate the domain logic, ensuring event processing remains testable and decoupled from infrastructure dependencies.

The best way to enforce inward dependencies is by structuring layers so Infrastructure depends on Application, which depends on Domain. This prevents outer concerns from leaking inward, ensuring the domain core remains isolated, testable, and maintainable across environments.

You should avoid hexagonal architecture for simple back-end systems with minimal complexity. The overhead of defining ports, adapters, and strict layered boundaries is best suited for large applications requiring high maintainability, parallel development, and clear bounded contexts.