ShareDB is a realtime database backend based on Operational Transformation of JSON documents.
ShareDB solves the problem of synchronizing shared state across multiple concurrent users in realtime. It uses Operational Transformation to merge conflicting edits from different clients into a consistent document state. The system maintains a log of all operations and applies them in a way that ensures eventual consistency even when edits arrive out of order. Clients can work offline and have their changes synced when they reconnect.
ShareDB suits applications requiring live collaboration on JSON documents, such as shared editors, whiteboards, or any multi-user editing scenario. It provides both synchronous APIs for immediate local feedback and asynchronous consistency guarantees across all connected clients. The tool includes realtime query subscriptions, middleware for access control, and projections to filter document fields. It can be deployed horizontally by integrating a pub/sub system and works equally well in browsers or on servers. The project includes in-memory implementations of its database and pub/sub layers for testing purposes, and provides access to historic document versions and realtime user presence syncing.
Development activity shows consistent engagement with the issue tracker for bug reports. The documentation is actively maintained as Markdown files and can be built and served locally using Jekyll. The project includes working examples demonstrating core functionality such as a counter and leaderboard application.
