Map matching

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.