Code Room
On-callHardoc-g297
Subject Dns failureLevel Senior–Staff~40 minCommon in Networking & APIs · Distributed systems interviewsIndustries Technology

Question

At 08:00 you added a new internal service, payments-v2.internal, and rolled out clients that call it. For ~20 minutes after the DNS record was created, a large fraction of clients keep failing with NXDOMAIN / 'no such host' for payments-v2.internal, even though the record clearly exists and `dig` from a fresh resolver returns it instantly. The failures slowly taper off on their own. Dashboards: the record's positive TTL is short, but the failures persisted far longer than that. Some clients started working at 08:05, others not until 08:18. How do you triage and what's the fix?

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
Loading whiteboard…
Run or narrate your approach, then ask the coach.