Database Design

Database design is about modeling reality correctly, then optimizing for access patterns. The mental model: (1) Model the data correctly first (normalization). (2) Optimize for your specific read/write patterns (indexes, denormalization). (3) Choose the right database type for the data model. Never pre-optimize before you understand access patterns. Why Database Design Matters Every application you'll ever build stores data. The difference between a system that handles 100 users and one that handles 100 million users often comes down to how you designed your database. Bad database design leads to: Slow queries (seconds instead of milliseconds) Data inconsistency (user sees stale data) Scaling nightmares (can't add more capacity) The Relational Model Most databases use the relational model invented by Edgar Codd in Data is organized into tables (relations), each with rows (records) and columns (attributes). Interview Tip When asked about database design, always start with: 'Let me first understand the read/write patterns and the relationships between entities.' This shows you think before you design. Python Implementation Java Implementation JavaScript/TypeScript Implementation