Consistent Hashing, explained.
Consistent hashing assigns keys to positions in a shared hash space so membership changes remap a limited portion under the ring rule.
Why it happens
Twenty fixed keys belong to the first clockwise server at or after their positions. Adding server fifty moves only keys in its preceding interval; the ledger compares original and new ownership.
Consistent hashing assigns keys to positions in a shared hash space so membership changes remap a limited portion under the ring rule.
Read the result
Compare original and current owners for each unchanged key. Remapping is limited by the ring rule, while balance is a separate question.
A worked example
Add a server inside one ownership interval
Inspect original server positions ten, thirty-five, sixty and eighty-five.
Add server fifty and identify keys between thirty-five and fifty that change owners.
Verify that keys elsewhere retain their original owners, including wraparound assignments.
OPTIONAL DEEPER DETAILGo deeper: inside the model
Inside this model
Twenty fixed keys belong to the first clockwise server at or after their positions. Adding server fifty moves only keys in its preceding interval; the ledger compares original and new ownership.
Where this idea is useful
A practical use
Plan a distributed-cache membership change while separating remapping cost from load balance.
A common misconception
“Limited remapping guarantees equal load on all servers.”
Remapping and balance are different properties. This small fixed ring lacks virtual nodes and supplies no balanced-load guarantee.
What this explanation leaves out
- The tiny deterministic ring has no virtual nodes, replication, adversarial keys or balanced-load guarantee. Keys and server positions are authored examples.
Why does a key larger than the final server wrap around?
The ordered space is a ring, so the first clockwise server after the endpoint is the smallest listed position.
Are you trying to minimise moved keys, balance work, or provide replication?
Associated thinkers
Associations marked provisional are awaiting source review.
Further reading
Explore the original research or the teaching reference behind this experiment.