High eviction rates signal that Memcached is running out of memory and removing cached items prematurely, leading to increased cache misses and database load.
A sudden drop in cache hit ratio exposes ineffective caching strategies, such as frequently missed keys never being stored, or cache restarts causing data loss.
Concentration of requests on a small number of 'hot keys' creates performance bottlenecks, as Memcached's single-threaded key access serializes high-volume reads.
Connection refused errors indicate Memcached is unreachable due to network misconfigurations, firewall rules blocking port 11211, or service unavailability.
Monitoring cache performance by key prefix reveals cache segments with low hit ratios or disproportionate memory consumption, indicating optimization opportunities or bugs.
