System designHardsd-g514

Subject Collaborative editingLevel Senior–Staff~55 minCommon in Code quality & review · Algorithms & data structures interviewsIndustries Technology, Software development

Question

Design the real-time engine behind a collaborative spreadsheet. Multiple users edit cells concurrently; cells contain formulas that reference other cells (A1 = B1 + SUM(C1:C100)). On any edit you must recompute exactly the dependent cells (not the whole sheet) and push results to all collaborators in real time. Sheets can have 1M cells, deep dependency chains, and cycles must be detected. Edits must converge across users.

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.