Video scrubbing previews
Design the video-scrubbing-preview (storyboard / sprite-sheet) and poster-frame system for a VOD platform. When a user hovers/drags the seek bar, the player must instantly show a thumbnail of the frame at that position across the whole timeline, for videos from 30s clips to 6-hour streams, on bandwidth-constrained clients. The platform also wants a good auto-selected poster frame per video. Design how previews are generated, packaged, and delivered, and how you keep client bandwidth and request count low.
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.