HLD-403·Messaging & Fan-out
Expert · 2,000 pts10M-Viewer Live Sports Broadcast Chat & Reactions
Design a stadium-scale live video chat and emoji reaction pipeline surviving 300k+ RPS goal-moment spikes on a single championship broadcast.
Max p99
≤ 80 ms
Availability
≥ 99.5%
Budget
≤ $9,200
Functional Requirements
- FR-1POST /streams/{stream_id}/chat — Ingests viewer chat messages and reaction bursts.
- FR-2GET /streams/{stream_id}/feed — Serves windowed room messages & aggregated reaction counts to edge gateways.
- FR-3PATCH & DELETE /streams/{stream_id}/chat — Updates, revokes, or deletes stream_id entries with bounded TTL or explicit cache/index invalidation.
- FR-4Must survive extreme single-room Zipfian skew and an 8x downstream storage latency brownout.
Workload Profile
Pre-Match Load95,000 Read RPS / 14,000 Chat Write RPS
Overtime Goal Peak260,000 Read RPS / 42,000 Write RPS (302k total)
Active Working Set48 GB live room ring buffers & reaction buckets
Contention ProfileExtreme alpha=1.35 skew on championship stream_id
Consistency Model
Bounded eventual fan-out (< 2s window) acceptable; requires salted/bucketed partitioning and brownout circuit breaking.
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