Private file uploads
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.
Clarify3:30 left
Estimate3:30 planned
Design10:00 planned
Deep dive8:00 planned
Failure5:00 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.