>I can't really argue whether his approach is good or not. The way he explains it seems like an extra useless layer that you're going to have to maintain to me though. So you have a RESTful PHP/whatever app returning JSON or the like. And then you have your front-end developers create a Node.js app that takes the PHP apps response and ends up rendering HTML or just returning that same JSON anyway?

I think there is value here. The way I see it: there are sometimes calculations that you want to perform on the server, but that are logically part of the UI layer. Maybe you need to aggregate the results of several service calls for a particular screen. Maybe you need to do an operation that's actually several steps.

You could do this all on the client side, of course, but that would perform badly, and might make e.g. security more complex. You could do it on the backend, but that results in a backend service that's tightly coupled to the UI - bad architecture, and possibly requiring close collaboration between two separated teams. By having a component that runs on the server, but belongs to the UI team (and therefore necessarily needs to be written in a language they understand), you get the best of both worlds.