{
  "status": "unknown",
  "advantages": [],
  "limitations": [],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-11-04",
  "slug": "paxos",
  "term": "Paxos",
  "aliases": [
    "Paxos consensus"
  ],
  "definition": "Paxos is a consensus protocol for choosing a single proposed value despite non-Byzantine process failures and unreliable message delivery.",
  "note": "A proposer first obtains promises and prior accepted proposals, then submits the required value for acceptance. It must retain the value from the highest-numbered accepted proposal in its phase-1 responses, if any. A chosen value and a value merely accepted by one node are different states. [paxos-simple]\n\nCrash recovery requires acceptors to retain promises and accepted-proposal state before replying. Quorum counts do not independently verify that this storage obligation was met. [paxos-simple]\n\nMulti-Paxos applies consensus to a sequence of slots and amortizes phase 1 across slots under a stable leader. A competing higher proposal can prevent that leader from progressing. Safety and eventual progress are separate properties. [paxos-simple]\n\nFlexible Paxos separates the phase-1 and phase-2 quorum families while preserving cross-phase intersection. It does not replace the promise and value-selection rules. [fpaxos]",
  "related": [
    "flexible-paxos",
    "quorum-intersection",
    "linearizability"
  ],
  "citations": [
    {
      "id": "paxos-simple",
      "title": "Leslie Lamport. Paxos Made Simple (2001), sections 2-3.",
      "url": "https://lamport.azurewebsites.net/pubs/paxos-simple.pdf",
      "accessed": "2026-11-04"
    },
    {
      "id": "fpaxos",
      "title": "Howard, Malkhi and Spiegelman. Flexible Paxos: Quorum Intersection Revisited. OPODIS 2016, LIPIcs 70 (2017), sections 3-7.",
      "url": "https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.25",
      "accessed": "2026-11-04"
    },
    {
      "id": "hesela-quorums",
      "title": "Hesela: Flexible Paxos phase availability, exact set examples and limits",
      "url": "https://hesela.com/analyses/replica-repair-coverage/#flexible-quorums",
      "accessed": "2026-11-04"
    }
  ],
  "provenance": [
    "Protocol semantics, not a device lifecycle; status is unknown and firstSeen is unset rather than assigning an invention date from a later explanatory paper."
  ]
}