The Real-time Collaboration Challenge
Build multiplayer features with WebSockets, presence indicators, conflict resolution, and offline-first architecture.
Build your unique collab
Same real-time patterns. Your unique, hilarious collaboration space.
The 10-day journey
Each day, a stakeholder email drops with new requirements. Just like real work.
Basic document management with REST API and optimistic updates.
Connection management, reconnection strategies, and message handling.
Show who's online, user avatars, and real-time status updates.
Receive changes from others and update the UI immediately.
Optimistic updates, server confirmation, and rollback handling.
Show where others are working with cursor and selection sync.
Two users edit same content. Handle conflicts gracefully.
Queue changes locally, persist across refreshes, work offline.
Drain queue properly, handle conflicts during sync, state reconciliation.
Connection status UI, error states, and production deploy.
What you'll actually learn
Not just how to build real-time features — but how to build one that doesn't fall apart at scale.
WebSockets
Real-time connections, connection management, reconnection strategies, and message queuing.
Conflict Resolution
Handle simultaneous edits gracefully with last-write-wins, server authority, or user choice patterns.
Presence
Show who's online, cursor positions, typing indicators, and real-time user activity.
Offline Support
Queue changes locally, persist to IndexedDB, sync on reconnect, and handle network failures.
Ready to build your unique collab?
Learn the architecture patterns that power Linear and Notion.
Other challenges
View allCheck out our other challenges to continue building your skills.