Adaptive bitrate streaming
Design the client-side adaptive-bitrate (ABR) system for a global VOD service streaming HLS to 200M devices spanning fiber to congested 3G. The goal is to maximize quality-of-experience: high average bitrate, near-zero rebuffering, few quality switches, and fast startup. Design the rendition ladder, the segment/manifest format, and the ABR decision logic, and explain how the player decides what to fetch next under changing throughput.
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.