hardreal_time
Design a Collaborative Editor (Google Docs)
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GoogleNotionFigmaLinearDropbox PaperCoda
Key Challenges
- ·Optimistic local edits with instant UI feedback and conflict-free rebase
- ·Operational Transformation (OT) or CRDT for conflict resolution
- ·Real-time presence, cursors, and selection synchronization via WebSocket
- ·Offline queue + deterministic reconnect catch-up without data loss
- ·Virtualized large document rendering with minimal re-renders
Key Takeaways
- ✓Separate local editor state from server-synced document state for instant typing.
- ✓Use operations (not full document) + baseVersion for optimistic updates and rebasing.
- ✓WebSocket is primary; HTTP fallback + versioned catch-up ensures reliability.
- ✓Presence and cursors must be ephemeral and throttled — never block the editing path.
- ✓Offline queue + IndexedDB + deterministic replay is what makes collaboration feel solid.