Steps to reproduce: Set up one mysql server. Set up one PHP application server (nginx+PHP fpm in my case, shouldn't make a difference with mod_php) on a different machine. Configure Wordpress to use said mysql server. Lock the database in some way (say, mysqldump of a Wordpress installation with millions of records in wp_options), then hit the application server with regular traffic (or ab), watch as load reaches pm.max_children. On the application server, not the database server.
¯\_(ツ)_/¯
Steps to reproduce: Set up one mysql server. Set up one PHP application server (nginx+PHP fpm in my case, shouldn't make a difference with mod_php) on a different machine. Configure Wordpress to use said mysql server. Lock the database in some way (say, mysqldump of a Wordpress installation with millions of records in wp_options), then hit the application server with regular traffic (or ab), watch as load reaches pm.max_children. On the application server, not the database server.