Every design decision involves tradeoffs. Discuss them.
SQL vs NoSQL:
- SQL: Strong consistency, complex queries, relationships
- NoSQL: Flexible schema, horizontal scaling, simpler for certain patterns
Caching:
- Pro: Faster reads, reduced database load
- Con: Data can be stale, adds complexity
Microservices vs Monolith:
- Microservices: Independent scaling, team autonomy
- Monolith: Simpler deployment, easier debugging for small teams
The magic phrase: "It depends on our requirements. If we need X, I'd choose A. If Y matters more, I'd pick B."
You don't need the right answer. Show you understand there isn't one.