HLD-236·Messaging & Queues
Medium · 1,000 ptsSkill-Based Live Support Ticket & SLA Queue Router
Design a Zendesk / Intercom support routing engine matching incoming customer tickets to online agents by language/skill while tracking SLA breach timers.
Max p99
≤ 60 ms
Availability
≥ 99.5%
Budget
≤ $5,400
Functional Requirements
- FR-1POST /tickets — Persists customer ticket, scores priority, and enqueues into skill queue.
- FR-2GET /queues/{tenant_id}/next — Assigns highest-priority waiting ticket to available support agent.
- FR-3PATCH & DELETE /tickets/{tenant_id} — Updates, cancels, or deletes tenant_id records and immediately invalidates or updates cached state (read-after-write).
- FR-4Must handle airline-cancellation ticket floods and survive primary DB node crashes.
Workload Profile
Business Hours Load24,000 Agent Poll RPS / 5,000 Ticket Event RPS
Outage Support Surge68,000 Read RPS / 16,000 Ticket Write RPS
Active Working Set18 GB active open tickets & agent availability
Traffic DistributionTenant hotspot on enterprise tenant_id experiencing outage
Consistency Model
Read-after-write ticket state transitions so two agents do not see stale unassigned status.
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