Code Room
On-callHardoc-g492
Subject Upstream timeoutLevel Senior–Staff~35 minCommon in Distributed systems interviewsIndustries Technology, Software development

Question

Your catalog service calls an upstream pricing service over HTTP. Starting 13:20, ~12% of product pages render with prices missing or showing $0.00, but your error rate is FLAT — no exceptions, no timeouts. Dashboards: the upstream returns HTTP 200 on the affected calls, but the response bodies are truncated or empty (your JSON parser silently yields a default-zero price rather than throwing). The upstream sits behind a load balancer that was reconfigured at 13:15 to add response buffering with a new max-body / idle-timeout setting. How do you triage and mitigate?

What a strong answer looks like

Stop the bleeding first (mitigate), then form hypotheses from real signals. Separate root cause from symptom, communicate status as you go, and close with what prevents a repeat.

Diagram & narrate the incident
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Run or narrate your approach, then ask the coach.