Notes on DDIA Chapters 5-6: Replication and Partitioning
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Replication (Ch. 5)
Three approaches, each with a different failure mode:
| Strategy | Failure mode |
|---|---|
| Single-leader | Leader outage = no writes |
| Multi-leader | Write conflicts need resolution |
| Leaderless | Read repair or anti-entropy needed |
The surprising takeaway: single-leader is still the right default for most systems. Multi-leader and leaderless are solutions to specific geographic or availability problems, not general upgrades.
Partitioning (Ch. 6)
Key insight: partitioning strategy determines operational complexity.
- Hash-based (by key hash): Simple, even distribution. Bad for range queries.
- Range-based (by key range): Good for scans. Risk of hotspots.
- Skewed partitions are the silent killer — one hot partition defeats the purpose.
What I learned
The chapter on partitioning changed how I think about database schema design. If you know your access pattern, you can choose a partition key that makes most queries hit one partition. If you don’t, hash partitioning is safer.