On-callMediumoc-g091

Subject Quota exhaustionLevel Mid–Senior~30 minCommon in Reliability & on-call interviewsIndustries Technology

Question

A routine autoscaling event during evening peak fails: new EC2 instances launch but stay `pending` then terminate, and your ASG activity log shows `Could not launch On-Demand Instances. VcpuLimitExceeded` for your instance family in us-east-1. Meanwhile pods elsewhere on EKS are stuck `ContainerCreating` with `failed to assign an IP address to container` in the kubelet logs. Traffic is up 40% over a normal Tuesday because of a marketing email that went out at 18:00. How do you triage this and restore capacity?

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.