What is consistent hashing and why is it important for distributed databases?

Consistent hashing maps both keys and nodes to positions on a virtual ring (0 to 2^32). A key belongs to the first node clockwise from its hash position. Advantage over naive modulo hashing (key % numNodes): When you add/remove nodes with modulo hashing: almost all keys remapped (massive data movement). With consistent hashing: only the keys in the affected range need to move (typically 1/N of dat