architecture-patterns

From README

Architecture Patterns When to Use What Simple (No Layers) Use when: Scripts, utilities, CLI tools, small services with minimal business logic, CRUD with no rules beyond validation. Structure: Functions or modules organized by feature. No layers, no ports. Tradeoff: Fastest to build. Hardest to extend if complexity grows. Refactor to layers when it hurts, not before. MVC (Model-View-Controller) Use when: Web apps, APIs, most CRUD-heavy applications. The default for Rails, Django, Express, Spring. Structure: Route -> Controller (thin, delegates) -> Service (business logic) -> Model/Repository (data). Dependency direction: Controller depends on Service, Service depends on Model. Never the reverse. Tradeoff: Familiar, well-tooled, lots of examples. Services can grow large as business logic gets complex. At that point, consider extracting a domain layer. Onion / Hexagonal Use when: Complex domain logic with many business rules. Multiple input channels (HTTP, CLI, events).