Note that caching didn't and wouldn't have significantly helped in this case. It was an inappropriate Apache configuration. No amount of caching will stop a s

Note that caching didn't and wouldn't have significantly helped in this case. It was an inappropriate Apache configuration. No amount of caching will stop a server from falling over when it's running far more Apache processes than it has RAM for. While caching is part of the solution, it's not the high bit (lowering MaxClients and properly configuring KeepAlives is).