Surge pricing

Design the surge/dynamic-pricing system for a ride-hailing platform. It must compute a per-area price multiplier from the live supply (available drivers) and demand (open requests + app-open intent) in that area, update every ~30s, stay stable enough to not whiplash riders, and be explainable/auditable for regulators. Cover the geo-aggregation, the pricing computation, and consistency across the rider/driver views.