Preventing App Performance Degradation Due to Sudden Ride Demand Spikes

Grab's engineering team faced a brutal problem: rain in Southeast Asia would crash their entire ride-hailing system. When demand spiked locally, users everywhere suffered.

Grab's engineers built the 'Spampede' filter, a circuit breaker inspired solution that prevents localized demand spikes from degrading app performance globally. The system intelligently throttles requests when supply can't meet demand in specific geographic areas.

Key Takeaways

• Uses Geohash algorithm to bucket locations without expensive API calls
• Redis INCR tracks unallocated requests with automatic TTL cleanup
• Intentionally drops bookings to protect system-wide availability
• Trades monitoring accuracy for throughput using time bucketing
• Processes requests before hitting downstream services to minimize load

The counterintuitive engineering decision that saved their business involves deliberately refusing customer requests, and the CAP theorem explains why it works.