System designHardsd-g702

Subject Network flow telemetry collector protocolLevel Senior–Staff~45 minCommon in Networking & APIs interviewsIndustries Telecom, Technology

Question

Design a network-telemetry / flow-record collector that ingests NetFlow/IPFIX/sFlow from 50,000 routers and switches, peaking at 5M flow records/sec over UDP. It must handle lossy UDP ingest, template-based decoding, high-cardinality aggregation (top talkers, per-prefix bytes), and serve both real-time anomaly detection and historical queries. How do you ingest, decode, aggregate, and store at this rate?

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.