Describe a time when applying SOLID principles improved your project.

Short answer: In a recent project, we had a monolithic service class handling multiple responsibilities, making it hard to maintain and extend.

Explain a bit more

By applying Single Responsibility Principle (SRP), we split the class into focused services, each with a clear purpose. This drastically improved readability, reduced bugs, and made it easier to add new features without risking regressions. The project became more testable because each small class could be unit tested independently.

Real-world example (ShopNest)

Open/Closed in ShopNest: add a new payment method by adding a class, not by editing a giant switch in CheckoutService.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.