You probably have to set it yourself: http://mamchenkov.net/wordpress/2016/08/04/504-gateway-timeout-error-on-nginx-fastcgi-php-fpm/
What is a bit strange is the 499 error which means that the client gives up before the server can send data. So it could be client-side as well (network connection, firewall, …), you could try to connect one of these clients to one of the test servers: Demo instances of 9-14 now live