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On-callHard
Question
A stream-processing consumer (Kafka → transform → write to a slow downstream warehouse) starts growing RSS and eventually gets OOMKilled, then on restart immediately reprocesses a backlog and OOMs again — a crash loop. Dashboards show consumer lag climbing for hours, an in-memory work queue between the fetch stage and the write stage growing without bound, and downstream warehouse write latency up 5x after the warehouse began a maintenance/compaction window. Consumer fetch rate is unchanged. Triage and fix.
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.
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