Per-title encoding optimization
Design the per-title (and per-shot) encoding-optimization service that decides the ABR ladder for each title rather than using one fixed resolution/bitrate ladder for the whole catalog. A flat ladder over-spends bits on simple content (a talking-head cartoon) and under-delivers on complex content (a fast-action sports clip). The service must analyze each title's complexity, choose the rungs (resolution+bitrate pairs) that sit on the quality-vs-bitrate convex hull, and do it cheaply enough to run on every one of millions of titles.
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.
Clarify5:00 left
Estimate5:00 planned
Design15:00 planned
Deep dive12:00 planned
Failure8:00 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.