I have a WP website with hundreds of visitors on it at any given time, like 250 to 300 concurrent visitors with millions of visits every month. I have the bigged Cloud server Hetzner providers with 16cores, and the website has gone down at least twice today with CloudFlare absorbing 5060% of the load and caching on images and static files.
What's the best way to utilize caching on the server? How can I make things faster? I have WP with WPSC installed on WO, but I don't know what other config I should be doing and WO is pretty much vanila setup?
Also, did I choose right or should I switch to a different caching engine?
Moreover, since we switched to Gillion theme (one of WP's fastest themes out there according to the developer: https://themeforest.net/item/gillion-multiconcept-blogmagazine-theme/19470306) the website is using much more CPU/MySQL load and we just cannot scale up anymore as already on biggest Cloud server Hetzner have.
Appreciate any feedback, thank you.