Complexity:?

Short answer: In large systems, managing many observers and keeping track of the relationships between subjects and observers can introduce complexity. It's important to manage subscription and unsubscription carefully to avoid memory leaks.

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.