[fast_404] Fast 404

But does Drupal core check anything else than missing files defined by the configuration fast_404.paths: '/\.(?:txt|png|gif|jpe?g|css|js|ico|swf|flv|cgi|bat|pl|dll|exe|asp)$/i'?

From Fast 404 module:

* The second is to check whether or not the URL exists in Drupal by checking
* with the menu router, aliases and redirects. If the page does not exist, we
* will serve a Fast 404 error and exit.