Code Room
On-callHard
Question
Your Cassandra cluster (write-heavy time-series telemetry) starts showing rising write latency and growing dropped-mutation counts at 04:00. Per-node metrics show pending compactions climbing into the thousands, SSTable counts per read exploding, disk IO at 100%, and tombstone warnings in the logs. A retention change last week switched a high-volume table from TTL-based expiry to periodic DELETE batches. How do you triage and stabilize this, and what's the durable 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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