Time Series Databases
Difficulty: Hard | Topic #29
What to Learn
Append-only write patterns, compression techniques (delta encoding, Gorilla compression), downsampling and retention policies, InfluxDB/TimescaleDB internals, querying time-range aggregations efficiently.
Resources
- Hello Interview: Time Series Databases ↗
- Arpit Bhayani: Compression Algorithm Powering Time-Series DBs ↗
- Ex-Google SWE: How Are Time Series Databases SO FAST? ↗
Covered by Problems
| Problem | Difficulty | Link |
|---|---|---|
| Activity Tracker (Strava) | Medium | → |
| Price Tracking Service | Medium | → |
| Metrics Monitoring System | Hard | → |
Key Concepts to Master
- Time-ordered append-only writes and why random updates are rare
- Gorilla compression — XOR delta encoding for floating-point timestamps and values
- Downsampling (roll-up) from raw to hourly to daily for storage efficiency
- Retention policies and tier storage (hot/cold)
- Columnar storage for time-range aggregations (avg, max, sum over windows)