[SomeCallMeTim]

Most web sites are just grabbing data from databases. If you use an async front-end, it's the database servers that need to scale, because they're doing the heavy lifting. But scaling your database infrastructure can be orthogonal to scaling the application layer; in Node, except for under extreme load, you may never NEED to scale the application layer. And for really high load situations, you may need 25-50x fewer Node servers than PHP.

It's the poor design of most systems that cause them to not scale; there are certainly exceptions where the server needs to do a lot of complex calculations, but those calculations can most of the time be handled in microservices and, again, scaled orthogonally to the application layer.