On-callMediumoc-g215

Subject Partial outageLevel Mid–Senior~30 minCommon in Reliability & on-call · Code quality & review interviewsIndustries Technology, Software development

Question

At 21:30 your video app's home screen fails to load for everyone, returning a 500. Dashboards: the personalization service (which supplies the recommended rows) has been erroring at 100% since 21:28 after a deploy; your home-screen API calls personalization synchronously and propagates its error instead of degrading; everything else (playback, search, account) is healthy. The home-screen API itself wasn't deployed. 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.

Learn the concepts

Diagram & narrate the incident

Loading whiteboard…

Run or narrate your approach, then ask the coach.