Real-time driver location and matching
Design the real-time location and matching backend for a ride/delivery platform. Millions of drivers stream GPS updates every few seconds; on a ride request you must find nearby available drivers within ~1s, then track the matched pair's live locations to the rider's app. Hot zones (a stadium letting out) create extreme local density. Updates are high-volume writes; proximity queries are latency-critical reads.
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.
Clarify5:30 left
Estimate5:30 planned
Design16:30 planned
Deep dive13:30 planned
Failure9:00 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.