If PHP-FPM is hanging adjust the /etc/php-fpm.d/www.conf
pm.max_children = 70
pm.start_servers = 20
pm.min_spare_servers = 20
pm.max_spare_servers = 35
pm.max_requests = 500
https://myshell.co.uk/blog/2012/07/adjusting-child-processes-for-php-fpm-nginx/