System designMediumsd-g563

Subject File uploadLevel Entry–Mid~30 minCommon in Storage & CDN interviewsIndustries Software development, Technology

Question

Design a file-upload feature for a small app where users attach documents (PDFs, images, up to ~20 MB) to records. Files must be stored durably, associated with the right record, and only the owner should be able to download them later. Upload volume is modest. Describe the upload flow, where files live, and how downloads are kept private.

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.