Earlier quoted context omitted.
> being hugged to death Whenever I read about this I can't help to think that people don't make a good use of a load balancer like HAProxy in front of their web-servers. Even if it's a single server behind the load balancer. There's this sweet spot where your server is handling requests as fast as it can but if you cross above it everything halts. To make it simple, this usually happens when one or more hardware reso…
I've actually dealt with this precise problem, HAProxy doesn't really solve the problem of an excess of traffic. At some point you'll start dropping connections or people will give up waiting. What you really want is something more like Varnish, a pass through caching proxy that handles known requests from memory, and any novel requests go through.
My opinion is that the CPU is usually the first to fall and you will not help it quite that much with an in-memory cache when the actual problem is the https overhead or the PHP/DB processing.