Two Plus Two Is Enough

Writes are serialized cluster-wide, so two clients updating the same key at once can never produce divergent versions

Since W+R exceeds N, the read set and the last acknowledged write set share a replica, so the newest value is among the responses

Every one of the three replicas holds the newest value by the time the write is acknowledged back to the client

Reads become linearizable with respect to concurrent writes, so the application never has to reconcile competing versions of a key