Mediator (ChatMediator):?

Short answer: The mediator manages communication between the users. It maintains a list of all users and broadcasts messages to all other users when one user sends a message. This keeps the users from directly knowing about each other, thus promoting loose coupling.

Real-world example (ShopNest)

Use a GoF pattern in ShopNest only when it removes duplication or makes a change safer—explain the problem it solves in the interview.

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.