ShareDB

ShareDB is a realtime database backend based on Operational Transformation (OT) for JSON documents. Version 0.13.3 is current, with active development and releases on npm. It features synchronous editing API with asynchronous eventual consistency, realtime query subscriptions, and horizontal scalability via pub/sub. Differentiators include OT-based conflict resolution, middleware for access control, and built-in reconnection and offline sync. It integrates with MongoDB and Redis for persistence and pub/sub.