On the new instance, a couple specific areas of Moodle are very slow. For example if we go into a course and click on a folder that has several images in it, it can take up to 30 seconds for a given image to load. Also, if you go to the list of all courses, it can take 30 seconds or so for the list to load.
Meanwhile last year's Moodle, which has a comparable number of courses and *much* more data in it, loads everything near instantly.
The targeted slowness is reproducible even off hours when the servers are under virtually no load whatsoever, so it doesn't seem to be a matter of being starved for resources. I've also been combing the admin screens one by one trying to find a difference between the two setups but am coming up with nothing there.The current one is running 3.1.2+ (Build: 20160915) while last year's is on 2.9.1 (Build: 20150706). The web and database server are both CentOS 7 with latest Apache and MariaDB currently available. As I mentioned earlier they are hosted on the same web server and same database server, so there is no difference in the server configuration and specs.
What should I be looking for to figure out why this year's instance has these issues compared to last?