What are the performance differences between interfaces and

Short answer: bstract classes? Abstract classes are slightly faster because they use direct method calls. Interfaces may incur slight overhead due to indirect method calls via vtable. Difference is usually negligible in most applications.

Real-world example (ShopNest)

Checkout calls IPaymentGateway.Charge(). Razorpay and Stripe adapters implement the same interface, so ShopNest can switch gateways without rewriting the order service.

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.