System designHardsd-g172

Subject Telemetry pipelineLevel Senior–Staff~40 minCommon in Distributed systems interviewsIndustries Technology

Question

Design the telemetry pipeline for a global edge/CDN network: 300 points-of-presence, each handling 200k req/s, that need per-request metrics (status, latency, cache hit/miss, origin, customer) centralized for billing and analytics. Sending one event per request to a central system is 60M events/s — far too expensive. You still need accurate per-customer billing counters and the ability to investigate latency by customer/region/status. Design edge-side aggregation, what you keep raw vs aggregated, and how you bound central cardinality and cost.

What a strong answer looks like

Clarify scale and constraints first. Propose a clean component breakdown, then go deep on the hard parts — data model, bottlenecks, consistency, failure modes — and name the trade-offs you are making.

Learn the concepts

Narrate your design

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Run or narrate your approach, then ask the coach.