Code Room
On-callHardoc-g581
Subject Cdn cache miss stormLevel Senior–Staff~35 minCommon in Storage & CDN interviewsIndustries Technology

Question

At 14:02 your origin fleet's request rate jumps 40x and origin CPU and DB connections saturate; the site slows to a crawl. The CDN dashboard shows cache hit ratio collapsed from 96% to 31% across all POPs simultaneously, and origin 5xx is climbing. Twenty minutes earlier, someone shipped a config change that appended a cache-busting query param to asset URLs, and separately a marketing email blast just went out driving a traffic spike. Multiple POPs are now requesting the same uncached objects from origin at once. How do you triage, stop the origin from melting, and fix the root cause?

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.