Resumable large-file upload
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.
Clarify4:00 left
Estimate4:00 planned
Design11:30 planned
Deep dive9:30 planned
Failure6:00 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.