Implementing Real-Time Conflict Resolution in Collaborative React Apps with CRDTs

Building collaborative applications where multiple users can edit the same data simultaneously is one of the most challenging problems in modern web development. Conflict-free Replicated Data Types (CRDTs) offer an elegant mathematical solution that guarantees eventual consistency without complex conflict resolution logic.

In this deep dive, we'll explore how to integrate CRDTs into React applications, examining both the theoretical foundations and practical implementation patterns that make real-time collaboration possible at scale.

Understanding CRDTs

CRDTs are data structures that can be replicated across multiple nodes in a distributed system, where each replica can be updated independently and concurrently without coordination. The key insight is that CRDTs are designed so that any conflicts from concurrent updates can be resolved automatically using mathematical properties.

There are two main types: state-based (CvRDTs) and operation-based (CmRDTs). State-based CRDTs synchronize by sending their entire state, while operation-based CRDTs only send the operations performed. For React applications, operation-based CRDTs are typically more efficient due to smaller payload sizes.

CRDT Types and Use Cases

Different CRDT types are optimized for different data patterns:

1. G-Counter (Grow-only Counter)
   • Perfect for like counts, view counts, or any monotonically increasing value.
   • Each node maintains its own counter; the total is the sum of all nodes.
2. LWW-Register (Last-Writer-Wins Register)
   • Stores a single value with a timestamp.
   • Useful for user preferences or simple state.
3. OR-Set (Observed-Remove Set)
   • Allows both adding and removing elements.
   • Ideal for collaborative lists, tags, or collections.
4. Y.Text / RGA (Replicated Growable Array)
   • Designed specifically for collaborative text editing.
   • Handles character insertions and deletions with proper ordering.

Integrating Yjs with React

Yjs is one of the most popular CRDT implementations for JavaScript. It provides a rich set of shared types and excellent React bindings.

Setting Up the Y.Doc

The Y.Doc is the root container for all shared data. Create it once at the application level and pass it down through React context. Each shared type (Y.Map, Y.Array, Y.Text) lives within this document and automatically synchronizes across all connected clients.

React Hooks for Yjs

Custom hooks like useYMap and useYArray subscribe to CRDT changes and trigger React re-renders. The key is to use the observe method to listen for changes and clean up subscriptions in the useEffect cleanup function.

WebSocket Provider

The y-websocket provider handles the network layer, automatically syncing changes between clients. It supports awareness features for showing cursor positions and user presence indicators.

Building a Collaborative Editor

Text Binding. Y.Text integrates seamlessly with popular editors like ProseMirror, Quill, and Monaco. The binding layer translates editor operations into CRDT operations and vice versa.

Undo/Redo Support. Yjs provides an UndoManager that tracks changes per-user, allowing each collaborator to undo their own changes without affecting others' work.

Offline Support. CRDTs naturally support offline editing. Changes made while offline are stored locally and automatically merged when the connection is restored.

Performance Optimization

As documents grow, CRDT performance becomes critical. Key optimization strategies include:

• Garbage Collection: Yjs includes built-in garbage collection to remove tombstones from deleted items;
• Lazy Loading: For large documents, load only the visible portion and fetch additional content as needed;
• Compression: Use the y-protocols encoding which provides efficient binary serialization, reducing network bandwidth by up to 90%.

Production Considerations

Deploying CRDT-based applications requires careful attention to several factors:

• Persistence: Use y-indexeddb for client-side persistence and y-leveldb or y-mongodb for server-side storage;
• Scaling: The WebSocket server can be horizontally scaled using Redis pub/sub for cross-instance communication;
• Security: Implement authentication at the WebSocket level and validate operations server-side to prevent malicious edits.