HLD-303·Geo & Telemetry
Hard · 1,500 ptsReal-Time Ride-Hail Driver Location & Dispatch
Design a high-write geospatial telemetry and nearby-driver discovery backend ingesting continuous 4-second GPS pings from active vehicles while matching riders during surge events.
Max p99
≤ 75 ms
Availability
≥ 99.5%
Budget
≤ $5,800
Functional Requirements
- FR-1PUT /drivers/{driver_id}/location — Ingests live lat/lng telemetry ping and updates spatial cell index.
- FR-2GET /riders/nearby?cell={geohash} — Returns closest available drivers within search radius.
- FR-3DELETE /drivers/{driver_id}/location — Supports tenant retention TTL expiry, rule updates, or stream cleanup while keeping recent rollup caches fresh.
- FR-4Must degrade cleanly without cascading queue pileups during a 7x downstream storage latency brownout.
Workload Profile
Baseline Commute30,000 Nearby Read RPS / 20,000 GPS Write RPS
Rainstorm Surge75,000 Read RPS / 52,000 GPS Write RPS
Active Working Set18 GB live spatial index cells
Hotspot ProfileDense airport & stadium geohash cell contention
Consistency Model
Eventual spatial freshness (< 3s GPS lag) acceptable for proximity search; trip dispatch state must remain durable.
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