Database Design for System Design Interviews
In every system design interview, you'll face the question: "How would you store this data?"
How you answer reveals a lot. The database layer is where many promising architectures fall apart. You can have perfectly designed APIs, elegant microservices, and beautifully orchestrated containers, but if your database can't keep up with your workload, none of that matters.
The database is often the hardest component to change later and the most expensive to get wrong.
The database is often the bottleneck. Design it wrong, and no amount of application-layer optimization will save you.
Database design in interviews isn't about memorizing SQL syntax or reciting the differences between PostgreSQL and MySQL.
It's about understanding trade-offs: consistency vs availability, read performance vs write performance, simplicity vs scalability. Every choice has consequences, and interviewers want to see that you understand what those consequences are.
In this chapter, we'll cover everything you need to know: SQL vs NoSQL, schema design, normalization, indexing, partitioning, sharding, replication, consistency models, transactions, query optimization, and real-world examples that tie everything together.