{
  "slug": "write-optimized-dictionary",
  "term": "Write-optimized dictionary",
  "aliases": [
    "Write-optimized index",
    "Write-optimized data structure",
    "WOD",
    "WOI",
    "WODS"
  ],
  "definition": "A write-optimized dictionary is a key-value data structure that defers and batches updates to amortize storage work while supporting queries.",
  "status": "shipping",
  "note": "The research category includes B-epsilon trees, LSM-trees and cache-oblivious lookahead arrays. It is not one file format, one filesystem or a synonym for a write-back cache. Families differ in their query and update bounds. [fast16]\n\nBuffering changes when work is performed, not whether correctness conditions apply. Compare the particular implementation's query, deletion, maintenance and durability behavior; the category name alone does not specify those contracts. [fast16]",
  "related": [
    "b-epsilon-tree",
    "lsm-tree",
    "buffered-upsert",
    "betrfs"
  ],
  "citations": [
    {
      "id": "fast16",
      "title": "Yuan et al. Optimizing Every Operation in a Write-Optimized File System. FAST 2016, sections 1-2; dictionary terminology and interface.",
      "url": "https://www.usenix.org/system/files/conference/fast16/fast16-papers-yuan.pdf",
      "accessed": "2026-11-04"
    },
    {
      "id": "hesela-buffered",
      "title": "Hesela: B-epsilon trees, visible updates and deferred work",
      "url": "https://hesela.com/analyses/b-epsilon-trees-buffered-updates/",
      "accessed": "2026-11-04"
    }
  ],
  "advantages": [],
  "limitations": [],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-11-04"
}