System designHardsd-g141

Subject MapsLevel Senior–Staff~50 minCommon in Distributed systems interviewsIndustries Technology

Question

Design a map-matching service that snaps noisy raw GPS trajectories onto a road network at scale — 100k trips/second of replay plus real-time streams — so that downstream traffic estimation and trip pricing use clean road-aligned paths. GPS is noisy (5–50m error), sparse in tunnels, and ambiguous at parallel roads/overpasses. Cover the algorithm, the road-graph access pattern, and the latency/accuracy trade-off.

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

Narrate your design

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Run or narrate your approach, then ask the coach.