How does the Strategy pattern promote Open/Closed Principle?

Short answer: It promotes the Open/Closed Principle by allowing you to add new strategies (algorithms or behaviors) without modifying the existing code. The context class uses an interface for the strategy, so new behavior can be added just by creating a new class that implements the interface—no need to touch existing logic.

Real-world example (ShopNest)

ShopNest payment fees use Strategy: IFeeCalculator with UPI/Card implementations chosen at runtime.

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.