What challenges do you face when refactoring for SOLID compliance?

Short answer: Challenges include: Legacy code with tight coupling, making decomposition hard. Risk of introducing bugs while splitting responsibilities or introducing abstractions. Managing dependencies and lifetimes correctly when injecting dependencies. Convincing stakeholders that refactoring time is valuable. Balancing between adhering strictly to SOLID vs. keeping code understandable and performant.

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.