Un-managed servers based on Apache have option to enable or disable modules accordingly. mod_expires and mod-headers are used for caching.
Tutorial on How to install and enable open source Apache on Linux operating system based web server.
Guide on how to update Apache server to latest version with all the security fixes using SSH terminal in Linux operating system.
DigitalOcean's WordPress admin installation is secured with htaccess. Read to know How to remove Apache password prompt for WordPress admin