Cache Hit Ratio Drop as Leading Indicator
warninglatencyUpdated May 9, 2025
Sudden drops in cache hit ratios (filterCache, queryResultCache, documentCache) precede query performance degradation. This indicates cache invalidation events, configuration changes, or query pattern shifts that require investigation.
Sources
How to detect:
Establish baseline cache hit ratios for each cache type (typically >70% for healthy systems). Alert on sudden drops >20% from baseline. Correlate cache ratio drops with query latency increases, commits, or schema changes.
Recommended action:
Investigate recent changes: commits that invalidated caches, query pattern changes, or schema updates. Add warmup queries for common access patterns. If cache sizes are inadequate, increase based on hit ratio analysis. Consider using cache=true for frequently filtered queries.