HLD-207·Geo & Telemetry
Medium · 1,000 ptsLive Food Delivery Order & Courier Status
Design an order lifecycle and live courier ETA status backend serving dinner-rush mobile app refreshes with instant state-transition accuracy.
Max p99
≤ 45 ms
Availability
≥ 99.5%
Budget
≤ $4,300
Functional Requirements
- FR-1PUT /orders/{order_id}/state — Updates kitchen prep, pickup, and courier milestone state.
- FR-2GET /orders/{order_id} — Polled by hungry customers viewing live order stage and ETA.
- FR-3PATCH & DELETE /orders/{order_id}/state — Updates, cancels, or deletes order_id records and immediately invalidates or updates cached state (read-after-write).
- FR-4State transitions (e.g. Picked Up -> Delivered) must be immediately visible without stale cached regressions.
Workload Profile
Baseline Lunch Load34,000 Read RPS / 5,000 State Write RPS
Friday Dinner Peak95,000 Read RPS / 14,000 Write RPS
Active Working Set22 GB active in-flight orders
Fault ScenarioPrimary order database crash mid-rush in Wave 3
Consistency Model
Read-after-write consistency required for order status transitions; automatic replica failover on node crash.
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