On-callMediumoc-g545

Subject Dns failureLevel Entry–Mid~20 minCommon in Networking & APIs interviewsIndustries Technology, Software development

Question

A service suddenly can't reach one of its dependencies. The logs show 'no such host' / name-resolution errors when it tries to call that dependency's hostname, while calls to other dependencies work fine. The dependency itself is up and reachable from a teammate's laptop by hostname. Your service didn't deploy. How do you triage this resolution failure?

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.