Code Room
On-callHardoc-g574
Subject Inference gpu autoscalerLevel Senior–Staff~35 minCommon in ML systems interviewsIndustries Technology

Question

Traffic to your GPU-backed LLM inference service rises 3x for a product launch. The HPA is configured to scale on CPU utilization, but CPU stays at ~35% while GPUs are pinned at 100% and p99 latency climbs and requests start timing out — yet no new pods are added. When you manually bump replicas, the new GPU pods sit Pending for several minutes before serving. Dashboards: GPU utilization 100%, GPU memory high, CPU low, cluster GPU node count flat, and a pending-pod count rising. Triage and stabilize.

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
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Run or narrate your approach, then ask the coach.