software-architecture

Clean architecture organizes code into distinct layers with clear boundaries—domain logic, application services, and infrastructure—where each layer has a specific responsibility. This separation prevents tight coupling, makes testing easier, and allows you to swap implementations without affecting core business logic.

Domain-driven design (DDD) prioritizes modeling the business domain first, then organizing code around that model; layered architecture separates technical concerns (presentation, business logic, data). DDD is more strategy-focused for complex domains, while layered architecture is more practical for structure. Both can work together—DDD informs what goes into each layer.

Decompose by identifying distinct responsibilities within the component, extract each into a separate module or function, and establish clear dependencies between them. Use early returns to simplify logic, remove duplication, and apply naming conventions that reflect each part's purpose. Test each part independently to ensure boundaries work correctly.

Prefer libraries when they solve a cross-cutting concern (logging, validation, HTTP handling) or a well-defined problem where the library is battle-tested and maintained. Building custom code is justified only when the library doesn't fit your domain boundaries or introduces unnecessary coupling to your core architecture.

Anti-patterns emerge when layers leak into each other, naming obscures intent, or concerns mix together. Enforce boundaries by preventing lower layers from depending on higher ones, use explicit naming that reveals purpose, separate domain logic from infrastructure code, and review refactoring opportunities early to catch violations before they spread.

DDD principles like clear naming and separation of concerns scale down effectively; you don't need the full strategic methodology. Start with clean architecture basics—defined layers, single responsibilities, and testable boundaries—and introduce DDD concepts only when domain complexity justifies the overhead.