On-callHardoc-p030

Subject Mitigation vs rootcauseLevel Senior~20 minCommon in Reliability & on-call interviewsIndustries Technology

Question

An internal dependency your service calls is degraded (slow, partial errors) but not fully down. You must decide whether to fail open (proceed without it) or fail closed (block). How do you reason about it?

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.

Learn the concepts

Diagram & narrate the incident

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Run or narrate your approach, then ask the coach.