HLD-415·Caching & Edge
Expert · 2,000 ptsGlobal Election & Olympics Live Scoreboard (300k-RPS Edge Feed)
Design a global live-results publishing & edge-delivery architecture (Olympics / World Cup / Election Night) where verified precinct/venue updates fan out to 50M+ concurrent viewers without stale regressions.
Max p99
≤ 42 ms
Availability
≥ 99.6%
Budget
≤ $11,600
Functional Requirements
- FR-1POST /results/{event_key}/publish — Commits signed monotonic sequence update and purges/pushes edge caches.
- FR-2GET /results/{event_key}/scoreboard — Serves sub-40ms p99 live tallies across CDN + regional cache tiers.
- FR-3PATCH & DELETE /results/{event_key}/publish — Updates, cancels, or deletes event_key records and immediately invalidates or updates cached state (read-after-write).
- FR-4Viewers must never see score/tally regressions (read-after-write monotonic version) even during DB failover.
Workload Profile
Live Coverage Baseline96,000 Scoreboard Read RPS / 4,500 Official Tally Write RPS
Finals / Call-Projection Peak275,000 Read RPS / 14,000 Tally Write RPS
Active Working Set36 GB live precinct/venue tallies & historical breakdowns
Traffic DistributionExtreme global herd on headline event_key scoreboards
Consistency Model
Monotonic read-after-write cache invalidation/write-through so refreshed scoreboards never revert to older tallies.
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