How to optimize memory and speed?

Hi,
I have a new installation with some websites. I migrated from CentOS with VestaCP to Debian 11 with HestiaCP.
I am very happy with the end result but it seems that my websites respond slightly slower than before.
However, it is on the same VPS server (5Gb ram).
How can I optimize the use of memory and the speed of the initial loading of the websites?
I know this is a complex question but maybe there are some best practices for HestiaCP?
Thanks.
Verus.

What is your setup? Nginx / Apache or Nginx only? Wordpress, other cms?

It is a basic setup with Apache and Nginx.
Websites are only wordpress. That’s about it.
Thnx.

It’s very little information to help you… speeding up WP can be very case dependant. In general I have the same setup with Nginx proxy. I feel I almost never need any additional caching plugins for my custom-build installs with as little plugins as possible. In some cases I use Cloudflare with a caching plugin.
The best thing to do is to analyse your websites to find the cause of the slowing down. Test your sites with: https://gtmetrix.com/, https://pagespeed.web.dev/ and the likes…

You can have 100 wordpress sites running in a machine or even 2 woocommerce sites running in that machine.

The optimization has nothing to do in this cases.