How does the Mediator pattern fit with SOLID and DI principles?

Short answer: Mediator decouples components by centralizing communication, supporting SRP and DIP by reducing direct dependencies. It fits DI because the mediator itself can be injected where needed. It supports OCP by allowing new communication routes or handlers without modifying existing components. Helps avoid tight coupling in complex workflows or CQRS patterns. Behavioral / Conceptual Questions

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.