How do you refactor a fat interface to follow ISP?

Short answer: Refactored Using ISP: public interface IWorkable

Example code

{ void Work(); }
public interface IFeedable
{ void Eat(); }
public interface ISleepable
{ void Sleep(); }
public class Human : IWorkable, IFeedable, ISleepable
{
public void Work() { }
public void Eat() { }
public void Sleep() { }
}
public class Robot : IWorkable
{
public void Work() { }
} ✅ Now each class implements only the interfaces it needs — in line with ISP. Inversion Principle (DIP)

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.