{
  "slug": "read-quorum",
  "term": "Read quorum",
  "aliases": [
    "Read response threshold"
  ],
  "definition": "A read quorum is a protocol-approved set of replicas whose responses satisfy the requirement for completing a read.",
  "note": "In an unweighted N-replica model, R is the response threshold, not necessarily a majority. Cassandra's named QUORUM level specifically requires a strict majority; local levels use a datacenter-specific scope. [cassandra]",
  "limitations": [
    {
      "text": "Meeting a response threshold does not by itself choose a real-time ordering of concurrent writes.",
      "citationIds": [
        "guarantees"
      ]
    }
  ],
  "related": [
    "write-quorum",
    "quorum-intersection",
    "read-repair"
  ],
  "citations": [
    {
      "id": "cassandra",
      "title": "Apache Cassandra 5.0.0: Dynamo architecture, tunable consistency and data versioning.",
      "url": "https://raw.githubusercontent.com/apache/cassandra/cassandra-5.0.0/doc/modules/cassandra/pages/architecture/dynamo.adoc",
      "accessed": "2026-10-13"
    },
    {
      "id": "guarantees",
      "title": "Apache Cassandra 5.0.0: Guarantees, including lightweight transactions.",
      "url": "https://raw.githubusercontent.com/apache/cassandra/cassandra-5.0.0/doc/modules/cassandra/pages/architecture/guarantees.adoc",
      "accessed": "2026-10-13"
    },
    {
      "id": "hesela-repair",
      "title": "Replica repair: what has actually converged?",
      "url": "https://hesela.com/analyses/replica-repair-coverage/",
      "accessed": "2026-10-13"
    }
  ],
  "status": "shipping",
  "advantages": [],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-10-13"
}