System designHardsd-g205

Subject Conflict resolutionLevel Senior–Staff~50 minCommon in Distributed systems interviewsIndustries Technology, Software development

Question

Design the sync engine for a collaborative document editor where users edit offline on phones/laptops and sync when reconnected. Two users can concurrently edit the same paragraph, and concurrent edits must merge without a server-side lock and without losing characters. Scale: docs up to a few MB, hundreds of collaborators per doc, sync over flaky mobile networks. Pick a conflict-resolution strategy and justify it against the alternative.

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.