What happens if a class has multiple responsibilities?

Short answer: If a class has multiple responsibilities: It becomes tightly coupled and harder to change without affecting other parts. Changes are more error-prone and often introduce bugs. Testing becomes harder since the class relies on multiple behaviors. Code reusability and readability suffer due to mixed concerns. You violate SRP, which makes code harder to maintain in the long run. Open/Closed Principle (OCP)

Real-world example (ShopNest)

Patterns in ShopNest should solve a real pain (swappable payments, test seams)—not be added for decoration.

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.