Consistent hashing and key-value stores

Consistent hashing maps keys and nodes onto a ring so adding a node moves a smaller portion of keys than a full modulo scheme. Virtual nodes can smooth uneven distribution, but the system still needs membership changes, replication, and hot-key protection.

Key-value design

Define the key format, value size, read and write operations, expiration behavior, and durability promise. Partition by a key that spreads load while keeping common operations local. Replicate according to availability and consistency needs, and make rebalancing measurable and reversible.