Quorum
A majority needed for a write or read to count.
Origin
Gifford's "weighted voting for replicated data" (SOSP 1979) introduced the R+W>N rule. The idea predates it in distributed databases literature (Thomas's 1979 majority consensus). Dynamo (2007) popularised tunable quorums in production.
Where it shows up in production
- Cassandra & DynamoDB Per-query consistency: ONE / QUORUM / ALL on reads and writes. Tune per workload.
- etcd & Raft Every commit needs an explicit majority — that's a quorum write. Reads can be linearizable or stale.
- MongoDB write concerns w:majority is a quorum write; reduces to majority of voting members in a replica set.
On Semicolony
Sources & further reading
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