Let’s say I have to host 25 websites… How do I know how powerful should my VPS be? Which specs it should have, how fast the connection should be to handle X visits per day?
How do you understand which are your system requirements BEFORE deploying a project? Do you just make estimates and then scale up? Or there’s some kind of tool to benchmark? how to handle this kind of stuff?
If on the public internet, also consider how your going to integrate with a CDN like Cloudflair. With luck they will serve a lot of the load and provide the DDOS protection.
Cloudflare scares me, they have way too much power. Maybe look for alternatives instead. Best case they are not from the USA, their demand for privacy and security is going down the drain faster than you can blink.
The point is a CDN is worth considering if your site cannot be down and it may be subject to high load or DDOS attacks. There are many CDNs.