I have siteA.com (live) and siteB.com (staging) which both are identical WordPress sites sitting in a single EC2 server using Webmin with CentOS, MySQL, PHP.
The issue is that when I perform the same booking on each site which calls the admin-ajax.php, it took siteA 13 seconds to complete the booking but only 2 seconds for siteB.
How could I troubleshoot to find out what's wrong with siteA?