SOLID Principles

Five principles by Robert C. Martin for maintainable, testable OOP design. Apply to backend services, repositories, controllers, and complex frontend components.

When to Use

• Designing class or service structures
• Identifying why code is hard to test or change
• Reviewing class responsibilities and dependencies
• Building plugin/extension systems

Don't use for:

• Simple scripts or utilities (<200 LOC)
• Prototypes or MVPs where speed > correctness
• Procedural code with no classes