AccentureObject-Oriented ProgrammingMedium
What is SOLID in object-oriented design?
SOLIDOOPDesign PrinciplesClean Code
Question
Explain SOLID principles briefly and why they matter in production systems.
Interview Answer
SOLID principles improve maintainability by reducing coupling, improving testability, and making code safer to extend. They help teams avoid rigid class hierarchies and bloated interfaces, which is critical when systems grow and multiple developers modify the same codebase.
Explanation
Each SOLID principle addresses a common design failure mode: rigid classes, fragile inheritance, bloated interfaces, and hard dependencies. In production, SOLID improves testability and lowers regression risk during feature changes.
Key Points
- SRP keeps classes focused
- OCP supports extension without risky edits
- LSP protects substitutability in inheritance
- DIP enables testable, loosely coupled architecture
Common Mistakes
- Treating SOLID as rigid rules instead of design guidance
- Applying abstractions prematurely
- Creating unnecessary interfaces with no variation point
Likely Follow-Up Questions
- Give a real-world SRP violation and fix.
- How does dependency injection support DIP?
- When can over-engineering happen with SOLID?
Interview Timing
Target speaking time: about 4 minutes.