Real-time collaborative editing
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.
Clarify5:30 left
Estimate5:30 planned
Design16:30 planned
Deep dive13:30 planned
Failure9:00 planned
Which questions mattered is sealed until you submit. Telling you now would just be handing over the edge cases.
Run or narrate your approach, then ask the coach.