Track 1 · Interview Foundations
Database Types Field Guide
Seven families of database, each built to answer one kind of question fast. This page tells you the question each one is good at, how each one breaks, and how to pick without arguing for an hour.
Guide28 min read
On this page
- The search that ate the checkout
- The simple version
- The one-glance matrix
- Relational: where money and seats live
- Key-value: the fastest answer is a known key
- Document: one read, one whole object
- Wide-column: relentless writes, read by key and time
- Graph: when the question is about the connections
- Time-series: a number, a timestamp, a few tags
- Search: a second index, not a second source of truth
- Which database makes which consistency choice
- Real engines, side by side
- The three engines everyone confuses
- Pick one: two desi systems
- Common traps