Consistent Hashing

Consistent hashing is a technique that minimizes data movement when nodes are added or removed from a distributed system. It's fundamental to how modern distributed databases, caches, and load balancers scale—and a favorite topic in system design interviews.

When you're designing any system that distributes data across multiple servers (database sharding, distributed caches, load balancers), the question of "how do we decide which server handles which data?" becomes critical. Consistent hashing provides an elegant answer.