How do you troubleshoot high read latency in ScyllaDB?

1. Check for wide partitions - a large partition takes longer to scan and can dominate latency for that key.
2. Check tombstone counts in query tracing - excessive tombstones force reads to skip past dead data.
3. Review the consistency level - QUORUM or ALL reads pay more coordination latency than ONE or LOCAL_QUORUM.
4. Look at SSTable count per read - a high count (common with STCS under heavy churn) suggests switching to LCS or tuning compaction.
5. Check cache hit rates - frequent misses on the row/key cache push more reads to disk.
6. Confirm the driver is shard-aware - a non-shard-aware driver adds an internal hop on every request.

ScyllaDB's built-in tracing (TRACING ON in cqlsh, or the Monitoring Stack's per-query breakdown) is usually the fastest way to see exactly where time is going for a specific slow query, rather than guessing from cluster-wide metrics alone.

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