Consistent Hashing

ELI5 — The Vibe Check

Consistent Hashing distributes data across servers so that when you add or remove a server, only a small fraction of data needs to move. Normal hashing? Add a server and EVERYTHING reshuffles. Consistent hashing? Only 1/N of data moves. It's how caches and databases scale without chaos.

Real Talk

Consistent hashing maps both keys and nodes onto a hash ring, assigning each key to the nearest node clockwise. When nodes are added or removed, only keys between the changed node and its predecessor are remapped. Virtual nodes improve balance. Used in distributed caches (Memcached), databases (DynamoDB, Cassandra), and CDNs.

When You'll Hear This

"Consistent hashing means adding a cache node only moves 1/N of the keys." / "DynamoDB uses consistent hashing to partition data across storage nodes."