System designMediumsd-g610

Subject Resumable large file upload storageLevel Mid–Senior~35 minCommon in Storage & CDN interviewsIndustries Technology, Software development

Question

Design a resumable large-file upload service for clients on flaky networks uploading multi-GB files (video, datasets, disk images). Constraints: uploads must survive dropped connections and resume without restarting, parts upload in parallel, the assembled object must be integrity-verified, partial/abandoned uploads must not leak storage forever, and the server should detect duplicate re-uploads cheaply. Cover the upload protocol, assembly, and cleanup.

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.