Consistent Hashing maps both servers and keys onto a circular hash space (ring).
Each key is assigned to the first server found by walking clockwise from its position.
Virtual nodes give each physical server multiple positions on the ring, improving load balance.
Why it matters: When a server is added or removed, only the keys between it and its predecessor are remapped — not all keys. This makes consistent hashing ideal for distributed caches, CDNs, and databases.