Photo storage with tiering
Design photo storage for a social product: users upload billions of photos, each original generating several derived sizes (thumbnail, feed, full), reads vastly outnumber writes and are heavily skewed toward recent uploads, and most photos are never viewed again after their first week. You need cheap storage at the long tail, fast delivery of hot photos, and an efficient way to manage the many small derived files. How do you store, serve, and tier this?
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.
Clarify4:30 left
Estimate4:30 planned
Design13:30 planned
Deep dive10:30 planned
Failure7:00 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.