System design interview question
Design a Global Real-Time Collaborative Document Editor Backend (Like Google Docs at Scale)
Design the backend system for a globally distributed collaborative document editing platform supporting 200M concurrent users with 50M active documents. The system must handle real-time synchronization of edits across multiple clients with sub-500ms latency, maintain consistent document state across regions, support undo/redo for individual users, and persist versioning history. Users can be geographically distributed, and documents must be accessible with consistent reads after writes. The platform must handle 100K concurrent edits per second across all documents while maintaining data durability and preventing conflicts. Consider how you'd handle offline-first capabilities, operational transformation or CRDT-based conflict resolution, and efficient storage of millions of revisions without unbounded growth.
Practice this question step by step with an AI interviewer that reviews your requirements, your architecture and your trade-offs, and scores the design.