On-callMediumoc-g539

Subject Queue backlogLevel Entry–Mid~20 minCommon in Distributed systems · Algorithms & data structures interviewsIndustries Technology, Software development

Question

A background worker consumes jobs from a queue (emails, image resizing) and normally keeps the queue near empty. The dashboard now shows the queue depth climbing steadily and the oldest message age growing — users report their actions are taking a long time to 'take effect.' Producers are enqueuing at the normal rate. The web tier is healthy. How do you triage why the backlog is growing?

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.