architecture-patterns

Structure the project into domain entities, use cases, adapters, and infrastructure layers with dependencies pointing inward. Define abstract repository interfaces in the domain layer and implement them in adapters, keeping business rules free of framework code.

Clean Architecture organizes code into concentric layers with an inward dependency rule, while Hexagonal Architecture centers the domain and connects it through ports and adapters. Both keep business logic independent of frameworks and infrastructure.

Define the repository as an abstract port interface in the domain layer, then inject a mock or in-memory adapter during tests. The use case depends only on the interface, so no real database connection is required.

Avoid full Clean Architecture for simple CRUD applications where the layering overhead outweighs the benefits. Over-engineering small services with entities, use cases, and adapters adds complexity without improving maintainability.

An anemic domain model contains entities with only data and no behavior, pushing business logic into services or controllers. Rich domain models place behavior alongside data, enforcing rules like order validation inside the entity itself.