> If you've ever seen an API gateway written using the same web framework as the other services, where in order to route "/external/order" to "/internal/order", the first step steps are e.g. "File | new | Controller", call it "ExternalController", make a GET method called "order", and in there code up a http call to "internal/order" ... you have a shantytown API gateway.

That's not a shantytown. That's an architecture astronaut utopia, creating according to the latest methodologies.