Yelp
Why uniform grids create hot shards, H3 and S2 hierarchical indexes, multi-attribute filtering with inverted indexes, boundary queries, and swapping a spatial index with zero downtime.
Uber
Location ingest at a million pings/sec, dispatch as a matching problem, surge from H3 supply-demand ratios, HMM map matching, and a trip state machine that survives dead zones.
Local Delivery
Global batch assignment with min-cost flow, decomposed ETA models, order batching, inventory accuracy, and the three-sided marketplace nobody mentions.
Strava
Polyline segment matching with R-trees and Fréchet distance, FIT file ingestion spikes, leaderboards in sorted sets, GPS and elevation noise, privacy zones, and anti-cheat.