Apache can be configured to run FastCGI with two modules: mod_fastcgi and mod_fcgid. The difference is that mod_fcgid passes just one request to the FCGI server at a time while mod_fastcgi passes several requests at once, the latter is usually better for PHP, as PHP can manage several request using several threads and opcode caches like APC usually work only with threads and not with processes. This means that using mod_fcgid you end up having many PHP processes which all have their very own opcode cache.”