Hi, is in-memory caching Nginx existing and enabled in Centmin mod ? ;)
You have to configure it in your nginx config/vhost config specifically for each web app you use i.e. wordpress, forums etc. Wordpress installer has some out of box caching setup Wordpress Nginx Auto Installer (WP Super Cache) and Redis server setup and redis caching for wordpress and xenforo is discussed and outlined at Redis - How to install Redis server on Centmin Mod LEMP stack | Centmin Mod Community