{
  "slug": "failover-slot",
  "term": "Logical failover slot",
  "aliases": [
    "PostgreSQL failover slot"
  ],
  "definition": "A PostgreSQL logical failover slot is a logical replication slot enabled for synchronization to a physical standby so consumption can resume after promotion.",
  "note": "The failover flag enables synchronization; it does not prove a usable copy exists on the target standby. [pg-failover] PostgreSQL 18 readiness requires a complete slot inventory and persistent, valid, synchronized copies. [pg-failover]",
  "status": "shipping",
  "advantages": [],
  "limitations": [
    {
      "text": "A temporary synchronized slot cannot support post-promotion continuation, and slot copying cannot restore WAL or catalog history already removed from the standby.",
      "citationIds": [
        "pg-decoding"
      ]
    },
    {
      "text": "Readiness is point-in-time evidence, not proof of fencing, exactly-once consumer effects or a universal zero-loss guarantee.",
      "citationIds": [
        "hesela-replication"
      ]
    },
    {
      "text": "Requesting an older LSN cannot rewind logical streaming before confirmed_flush_lsn; a reconnect alone does not establish that missing consumer history was replayed.",
      "citationIds": [
        "pg-logical-start"
      ]
    }
  ],
  "related": [
    "replication-slot",
    "logical-decoding",
    "hot-standby-feedback",
    "replication-lag",
    "idempotency"
  ],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-10-16",
  "citations": [
    {
      "id": "pg-failover",
      "title": "PostgreSQL 18: logical replication failover",
      "url": "https://www.postgresql.org/docs/18/logical-replication-failover.html",
      "accessed": "2026-10-16"
    },
    {
      "id": "pg-decoding",
      "title": "PostgreSQL 18: replication slot synchronization",
      "url": "https://www.postgresql.org/docs/18/logicaldecoding-explanation.html#LOGICALDECODING-REPLICATION-SLOTS-SYNCHRONIZATION",
      "accessed": "2026-10-16"
    },
    {
      "id": "hesela-replication",
      "title": "Hesela: Replication acknowledgements and logical failover readiness",
      "url": "https://hesela.com/analyses/replication-acknowledgements-durability-lag/",
      "accessed": "2026-10-16"
    },
    {
      "id": "pg-logical-start",
      "title": "PostgreSQL 18: START_REPLICATION SLOT LOGICAL and confirmed_flush_lsn",
      "url": "https://www.postgresql.org/docs/18/protocol-replication.html#PROTOCOL-REPLICATION-START-REPLICATION-SLOT-LOGICAL",
      "accessed": "2026-10-16"
    }
  ]
}