architecture

Clean Architecture, Domain-Driven Design, and backend system-design guidance: organizing a codebase into layers with the right dependency direction, choosing structural design patterns (Repository, Strategy, Observer, Command, DI), applying DDD tactical patterns (entities vs value objects, aggregates), designing REST resources and status codes, persistence (unit-of-work, N+1), caching, domain events, layered error handling, and recording decisions as ADRs. Use when designing a new system or feature, deciding which layer code belongs in, refactoring a tangled/God-object codebase, reviewing coupling and boundaries, shaping an API, or writing an Architecture Decision Record.