Database Fundamentals

Every system design interview involves at least one database. The question is never "should I use a database?" It's "which type, and why?" To answer that well, you need to understand what databases do under the hood: how they store data, guarantee consistency, and handle concurrent access.

This lesson covers the foundational concepts: ACID, storage engines, transactions, and the database categories you'll choose between. The next lesson goes deeper into SQL vs NoSQL trade-offs.