Cache Miss Rate Amplifying Read Latency
warningWhen cassandra_key_cache_hit_rate drops significantly below historical baseline, reads bypass cache and hit disk directly, multiplying I/O load and latency. This often correlates with workload changes or cache size misconfiguration.
Track cassandra_key_cache_hit_rate trending downward or consistently below 80%. Correlate with rising cassandra_client_request_read_time_50p and _99p percentiles. Verify with cassandra_sstable count per read increasing (more disk accesses per query). Check for workload pattern changes indicating new query types or data access patterns.
Analyze query patterns to identify if new access patterns are causing cache misses. Increase key_cache_size_in_mb in cassandra.yaml if memory permits. Review cache save periods and warm cache after restarts. Use nodetool info to verify cache usage. If workload has fundamentally changed, consider data model adjustments to improve query locality.