Design a tRPC API for Collaborative App

Design a tRPC API for a real-time collaborative application like Notion or Figma with documents, comments, and presence.

Functional Requirements

• Document CRUD and versioning
• Real-time collaborative editing
• Comments and threads
• User presence indicators
• Permission sharing
• Activity history

Non-Functional Requirements

• Sub-second sync latency
• Conflict resolution
• Offline support considerations
• Optimistic updates
• Efficient diff syncing

Questions to Consider

• How do you handle concurrent edits?
• What subscription patterns support presence?
• How do you structure procedures for optimistic updates?