Real-time location matching
Design the real-time location-tracking and matching system for a ride-hailing / delivery platform. 2M drivers send GPS pings every 4 seconds; riders request a ride and must be matched to a nearby available driver within ~1 second; riders also watch their matched driver's marker move live on a map. The 'find nearest available drivers' query runs constantly and must be fast over a moving 2M-point set. How do you index moving locations, run proximity matching at scale, and stream the live driver position to the rider?
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.