On my other website which is had quite high traffic with 47.000++ members, i used several layers of cache to handle traffic spikes. My software specs are running on WordPress 5.5, PHP 7.4.5, MariaDB 10.5.5, Centos 7 with Sentora Panel, Apache Web Server and PHP-FPM Server for PHP Handler.
- Opcache, first thing first, this module of PHP must be installed on your system.