# derbyjs/racer

Realtime model synchronization engine for Node.js

Repository: https://github.com/derbyjs/racer
Canonical: https://ross.abutalabs.com/products/derbyjs-racer
Language: TypeScript
License Family: other
Last push: 2025-08-27T23:07:33+00:00

## Health v2 (maintenance only)
Score: 42/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 39, release rhythm 13, longevity 100
- inputs: {"age_days": 5548, "days_push": 371, "days_rel": 371, "gap_med": 348, "n_releases_24m": 2}
- flags: no_license
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 1186, forks 117 (observed 2026-08-28T04:03:55.175446+00:00)

## What it is
Racer is a realtime model synchronization engine for Node.js built on ShareDB, providing a unified model and event interface for servers and browsers. It uses Operational Transformation for conflict resolution, supports realtime query subscriptions, offline operation, and persistent storage (e.g., MongoDB).

## Use cases
- build collaborative text editors with realtime multi-user editing
- sync application state between browser clients and Node.js servers in realtime
- support offline edits that automatically sync on reconnect
- subscribe clients to specific queries or documents with live updates
- scale realtime apps horizontally across multiple servers with PubSub
- render initial page state on the server and reinitialize the same model in the browser

## When to choose
- you need multi-user realtime collaboration with automatic conflict resolution
- your app must keep working offline and sync changes later
- you want one model API shared between server rendering and client interaction
- you're building with Derby or ShareDB and need a higher-level model layer

## When to avoid
- you only need simple REST APIs without realtime sync
- you use databases other than MongoDB and don't want to write a ShareDB adapter
- you need built-in, production-ready access control (still under development)
- you prefer a batteries-included framework rather than a model synchronization layer

## Facets
- artifact type: library
- maturity: active
- function: state-management, websocket, middleware, serialization
- domain: web-development, microservices, backend
- platform: browser
- tags: realtime-sync, operational-transformation, sharedb, offline-first, collaborative-apps, pubsub, real-time, nodejs, javascript

## Member repositories
- derbyjs/racer (main) score 42

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:03:55.175446+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 2026-08-30T06:23:53.324440+00:00, confidence not recorded.
  - readme: https://github.com/derbyjs/racer (fetched 2026-08-28T04:03:55.175446+00:00, sha 3b0b5b3934b8)
  - registry_npm: https://registry.npmjs.org/racer (fetched 2026-08-29T12:30:56.661556+00:00, sha df7d87873944)
- Data as of 2026-08-30T08:39:29.467469+00:00.