architecture-paradigm-layered

# The Layered (N-Tier) Architecture Paradigm ## When to Employ This Paradigm - When teams need clear architectural boundaries and a familiar structure for moderate-sized systems. - When compliance or operations teams require clear separation of concerns (e.g., UI vs. domain logic vs. persistence). - When the deployment artifact remains a monolith, but code clarity and separation are degrading. ## When NOT To Use This Paradigm - When high scalability demands require independent scaling of components - When multiple teams need independent deployment cycles - When complex business logic requires frequent cross-layer communication - When microservices architecture is already planned or in place - When real-time processing requirements make layered communication too slow ## Adoption Steps 1. **Define the Layers**: Establish a clear set of layers. A common stack includes: Presentation -> Application/Service -> Domain -> Data Access. 2. **Enforce Dependency Direction**: Code in a given layer may only depend on the layer immediately below it. Forbid any "upward" dependencies or imports. 3. **Centralize Cross-Cutting Concerns**: Implement concerns like logging, authentication, and validation as centralized middleware or policies, rather than duplicating this logic in each layer. 4. **Test Each Layer Appropriately**: Apply testing strategies suitable for each layer, such as unit tests for the domain layer, service-layer tests for orchestration logic, and integration tests for persis...