When should you NOT use consistent hashing?
If your cluster size is truly fixed and never grows, or if rebalancing is cheap, consistent hashing adds complexity for little gain. It shines only when you scale up/down frequently (Cassandra, DynamoDB, Redis Cluster) or can't afford cache wipes (Discord's chat cache, ride-hailing surge boundaries). For a fixed 3-node Postgres replica set, stick with traditional hash mod N.
Answered in
When 87% of Your Cache VanishesConsistent hashing maps nodes and keys to a circle, so adding a server moves only 1/N of keys instead of almost all of them.
Read the full analysisOther questions this article answers
More system design questions
- Why doesn't Google just run Dijkstra faster?
- What is a shortcut edge and when is it precomputed?
- How much space do shortcut edges take compared to the original graph?
- Can Contraction Hierarchies handle dynamic graphs like traffic or road closure?
- Why contract low-degree nodes first instead of high-degree ones?
- What is a CRDT and why does it matter for real-time collaboration?
- How do CRDTs handle concurrent edits without a central server referee?
- Why did Figma move from operational transforms to CRDTs?
Every answer on Crashtech is written by the editor of the article it comes from — never auto-summarised. Browse all answers or the System Design beat.