Challenges

Place nodes and keys on a hash ring; each node owns many small arcs

N=3 replicas clockwise on the ring; a read needs R acks, a write needs W

Each value carries [node, counter] pairs so concurrent writes are detected

If a replica is down, the next healthy node takes the write and hands it back later

Replicas compare hash trees of key ranges and sync only the differing buckets

Nodes exchange heartbeat tables with random peers

Append writes to a log, buffer in memory, flush sorted immutable files; Bloom filters guard reads

Simple modulo partitioning across the current server count

Wait for every replica to ack before returning success

Every request asks one coordinator which node owns the key