Calls from our pods to a payment API had 40 to 200 ms of unexplained latency and CoreDNS was the busiest workload in the cluster. Every lookup of api.payments.example went through five search domains first because of ndots:5. FQDNs with a trailing dot and a lower ndots fixed both.
A practitioner's reading of AWS's official summary of the October 19-20, 2025 us-east-1 disruption: a race in DynamoDB's DNS automation left an empty record, and recovery cascaded through EC2, NLB and Lambda. What happened per the report, and what we changed.
We moved our app to a new host and switched DNS on a Saturday. A day later almost half of requests still reached the old server. A 24-hour TTL, a nameserver change with a 48-hour delegation TTL and an old zone left online kept stale answers alive. This is the postmortem.