Your server doesn’t scale. Or, if you have a bigger site, then your servers (plural) don’t scale. They don’t scale ever. Servers in a classical sense are physical devices. They are made of up hardware components, and each of those components has an ability to do some task at some speed, and that’s it. Nothing anywhere gains any sort of capacity in response to the amount of stuff it’s being asked to do. It’s not scaling, and it’s never going to.