{
  "slug": "harmonia",
  "term": "Harmonia",
  "aliases": [
    "Harmonia in-network conflict detection"
  ],
  "definition": "Harmonia is a replicated-storage research architecture that uses a programmable switch to detect read-write conflicts and route eligible reads to individual replicas.",
  "note": "Absence from the dirty set is insufficient. The recipient also checks progress against the read's commit stamp. Read-ahead and read-behind integrations use opposite comparison directions. [harmonia-paper]\n\nThe design requires one active scheduler and ordered writes; an untrackable write is dropped rather than forwarded unseen. It is not a generic load-balancer configuration. [harmonia-paper]\n\nHesela's six synthetic witnesses isolate the receiver predicates; they do not reproduce a cluster or prove protocol correctness. [hesela-witness]",
  "status": "research",
  "advantages": [],
  "limitations": [],
  "related": [
    "craq",
    "chain-replication",
    "linearizability"
  ],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-11-09",
  "citations": [
    {
      "id": "harmonia-paper",
      "title": "Hang Zhu et al.: Harmonia, PVLDB 13(3), 375-388 (2019), sections 6-8; DOI 10.14778/3368289.3368301",
      "url": "https://www.microsoft.com/en-us/research/wp-content/uploads/2020/05/harmonia-vldb20.pdf",
      "accessed": "2026-11-09"
    },
    {
      "id": "hesela-witness",
      "title": "Hesela: synthetic receiver-predicate inputs, outputs and code hash",
      "url": "https://hesela.dev/research/harmonia/results.json",
      "accessed": "2026-11-09"
    },
    {
      "id": "hesela-replication",
      "title": "Hesela: a clean routing decision can expire in transit",
      "url": "https://hesela.com/analyses/replication-acknowledgements-durability-lag/#harmonia",
      "accessed": "2026-11-09"
    }
  ],
  "provenance": [
    "Primary-source review; original predicate examples, not hardware or distributed-protocol validation."
  ]
}