varnish_cache_hitpass

High rates of hitpass in Varnish suggest requests are bypassing cache and hitting the backend directly, potentially overloading Apache or other upstream servers. This commonly occurs when cache policies are misconfigured or when content is marked as uncacheable.

Apache prefork MPM's process-per-connection model becomes memory-inefficient when fronted by Varnish, as cache misses can trigger sudden process spawn bursts that exhaust available RAM and force swapping.