# BurntSushi/fst

Represent large sets and maps compactly with finite state transducers.

Repository: https://github.com/BurntSushi/fst
Canonical: https://ross.abutalabs.com/products/fst
Language: Rust
License: Unlicense
License Family: permissive
Last push: 2024-09-25T20:46:04+00:00

## Health v2 (maintenance only)
Score: 32/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 0, release rhythm 35, longevity 100
- inputs: {"age_days": 4016, "days_push": 707, "days_rel": null, "gap_med": null, "n_releases_24m": 0}
- flags: no_releases
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 2113, forks 146 (observed 2026-08-28T04:06:14.679446+00:00)

## What it is
A Rust library implementing ordered sets and maps using finite state transducers, enabling compact storage of billions of string keys with fast searchable queries. It supports memory-mapped access, range queries, Levenshtein fuzzy search, and regex automata integration.

## Use cases
- store billions of string keys compactly
- fast range queries over large dictionaries
- fuzzy string search with levenshtein automata
- memory-mapped searchable key-value sets
- build compact term dictionaries for search engines

## When to choose
- you need to index very large sets/maps of strings with minimal memory
- you want fast fuzzy or range queries over static key data
- you're building search or autocomplete infrastructure in Rust

## When to avoid
- you need frequent mutation of the set or map after building
- your keys are few or small enough for standard HashMap/BTreeMap
- you need rich value types rather than compact integer payloads

## Facets
- artifact type: library
- maturity: stable
- function: search-engine, data-science, serialization
- domain: developer-tools, databases
- platform: rust, cross-platform
- tags: finite-state-transducers, automata, memory-mapped, compact-data-structures, fuzzy-search, ordered-sets, ordered-maps, search, algorithms

## Member repositories
- BurntSushi/fst (main) score 32

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:06:14.679446+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T02:53:29.958719+00:00, confidence not recorded.
  - readme: https://github.com/BurntSushi/fst (fetched 2026-08-28T04:06:14.679446+00:00, sha a8bd07388667)
  - registry_crates: https://crates.io/api/v1/crates/fst (fetched 2026-08-29T10:33:30.819341+00:00, sha 25c173e9ede8)
- Data as of 2026-08-30T08:39:29.467469+00:00.