architecture-patterns

To structure a backend service with clean architecture, you define inward-pointing dependency layers starting with domain entities, use cases, and abstract ports, followed by interface adapters and outer infrastructure. This isolates business logic from frameworks and databases.

Refactoring a tangled monolith involves identifying where business rules have leaked into controllers or ORMs, then applying domain-driven design bounded contexts and dependency inversion to break cycles and isolate core logic into testable modules.

Designing bounded contexts for domain-driven design involves modeling aggregates, value objects, and domain events, then defining repositories and use cases to enforce clear module boundaries and prevent cross-domain dependency leaks.

Yes, you can unit test backend business logic without a running database by implementing in-memory adapters for your repositories and ports. Hexagonal architecture ensures external systems can be swapped without changing the core domain logic.

You need hexagonal architecture when you want to decouple core business logic from delivery layers and external systems. It is ideal for new microservices or monolith refactoring where testability and dependency cycle debugging are primary concerns.

Backend dependency cycles occur when outward infrastructure layers like frameworks or ORMs are directly referenced by inner domain logic. Enforcing inward dependency rules and abstract ports breaks these cycles by forcing external interactions through interface adapters.