Code Room
System designHard
Question
Design the rider-to-driver matching service for a ride-hailing platform operating in 200 cities, peaking at 30k ride requests/second globally with ~3M drivers broadcasting GPS updates every 4 seconds. A request must return up to 10 candidate drivers within ~2km in under 150ms p99, and a driver must never be offered to two riders at once. Walk through the geo-index, the dispatch loop, and how you keep consistency under concurrent matches.
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.
Learn the concepts
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Run or narrate your approach, then ask the coach.