# jonhoo/left-right

A lock-free, read-optimized, concurrency primitive.

Repository: https://github.com/jonhoo/left-right
Canonical: https://ross.abutalabs.com/products/left-right
Language: Rust
License: Apache-2.0
License Family: permissive
Topics: concurrency, multithreading, lock-free, rust
Last push: 2026-08-08T18:01:13+00:00

## Health v2 (maintenance only)
Score: 75/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 96, release rhythm 35, longevity 100
- inputs: {"age_days": 3497, "days_push": 25, "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 2277, forks 112 (observed 2026-08-28T04:06:33.493929+00:00)

## What it is
Left-right is a Rust concurrency primitive that maintains two copies of a data structure so many readers can access one copy in parallel while a single writer updates the other. It shifts synchronization overhead to the writer, letting reads scale linearly with core count when writes are infrequent.

## Use cases
- read-heavy shared data structure with a single writer in Rust
- lock-free concurrent reads over a map or config
- scale reads linearly across cores without reader coordination
- replace RwLock for read-mostly workloads
- share frequently-read, rarely-written state across threads

## When to choose
- your workload is read-dominated with one writer
- you need minimal coordination among readers
- you're in Rust and want a battle-tested concurrency primitive

## When to avoid
- writes are frequent (doubled memory and write cost dominate)
- multiple writers are required
- memory overhead of duplicating the data structure is prohibitive

## Facets
- artifact type: library
- maturity: stable
- function: concurrency
- domain: developer-tools, performance
- platform: rust, cross-platform
- tags: lock-free, read-optimized, single-writer, concurrency-primitive, rust-crate, algorithms

## Member repositories
- jonhoo/left-right (main) score 75

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:06:33.493929+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 2026-08-30T02:41:26.460835+00:00, confidence not recorded.
  - readme: https://github.com/jonhoo/left-right (fetched 2026-08-28T04:06:33.493929+00:00, sha 2c130c138fc6)
  - registry_crates: https://crates.io/api/v1/crates/left-right (fetched 2026-08-29T10:21:49.944886+00:00, sha 956ad4af0ab2)
- Data as of 2026-08-30T08:39:29.467469+00:00.