What design pattern would you use to decouple a complex system and why?

Short answer: The Mediator Pattern centralizes communication between components, preventing direct dependencies and reducing complexity. It promotes loose coupling and simplifies interactions. Alternatively, the Observer Pattern enables event-driven decoupling, and Facade Pattern provides a simplified interface to complex subsystems.

Real-world example (ShopNest)

Patterns in ShopNest should solve a real pain (swappable payments, test seams)—not be added for decoration.

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.