System designHardsd-g329

Subject Traffic shapingLevel Senior–Staff~45 minCommon in Distributed systems interviewsIndustries Technology

Question

Design the ingress queueing and shaping for a webhook-delivery system that must deliver events to thousands of customer endpoints with wildly different processing speeds — some endpoints respond in 50ms, others in 10s, and some are down for hours. A naive shared queue lets slow/dead endpoints clog delivery for fast ones (head-of-line blocking across customers). Design the queueing model, per-endpoint shaping and backoff, how you isolate slow consumers, and how you bound memory/queue growth when an endpoint is down for a long time.

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.