HLD-318·Geo & Telemetry
Hard · 1,500 ptsLive Road-Segment Traffic Telemetry & Partitioned ETA Engine
Design Uber / Google Maps’ real-time ETA engine ingesting continuous driver speed probes onto partitioned road-graph tiles and serving low-latency route ETAs.
Max p99
≤ 45 ms
Availability
≥ 99.5%
Budget
≤ $8,500
Functional Requirements
- FR-1POST /traffic/probes — Aggregates live GPS speed telemetry onto road segment tile_id weights.
- FR-2GET /eta/compute?tile={tile_id} — Evaluates contraction-hierarchy / road-tile edge weights under 45ms p99.
- FR-3DELETE /traffic/probes/{tile_id} — Supports tenant retention TTL expiry, rule updates, or stream cleanup while keeping recent rollup caches fresh.
- FR-4Must sustain rush-hour traffic storms and survive primary road-state shard crashes.
Workload Profile
Midday Traffic50,000 ETA Read RPS / 15,000 Probe Write RPS
Evening Rush Hour Peak135,000 Read RPS / 34,000 Probe Write RPS
Active Working Set32 GB metropolitan road-graph edge speed tables
Traffic DistributionDense spatial skew on downtown & airport corridor tile_id shards
Consistency Model
Bounded eventual road-weight updates (< 5s traffic lag) cached in regional tile memory.
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