Uber: the right car in under 3 seconds

How Uber matches a rider to a driver in under 3 s while ~500K driver pings a second land at peak: live locations as soft state in an H3 hexagon index in Redis, trips created exactly once in Spanner, ETA-led scoring with one PENDING offer at a time, per-cell smoothed surge, and a failover that replicates trips and rebuilds locations.