System designHardsd-g012

Subject Collaborative editingLevel Senior–Staff~50 minCommon in Distributed systems interviewsIndustries Software development, Technology

Question

Design the real-time collaborative editing engine for a shared rich-text document (think Google Docs / Notion page) where up to ~100 people can edit simultaneously, including offline editing that syncs on reconnect. Requirements: everyone's view converges to the same final document, no edit is silently lost, latency feels instant locally, and the document survives a server restart. Discuss your concurrency-control approach and its trade-offs.

What a strong answer looks like

Clarify scale and constraints first. Propose a clean component breakdown, then go deep on the hard parts — data model, bottlenecks, consistency, failure modes — and name the trade-offs you are making.

Learn the concepts

Narrate your design

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Run or narrate your approach, then ask the coach.