Stever, thank you very much for this editorial. Where I work all applications are 2-tier applications. Just the UI and the database. In previous jobs I would write APIs to help with the load, as well as separating work responsibilities into different layers. (Separation of concerns.) I've never understood why there isn't even one application where I work, that isn't separated into multiple layers. Especially as some of them are meant to be used by thousands of people at the same time.
Anyway, the important thing, for me, is that you've pointed out that a simple, naïve approach to writing API's without any thought towards scalability, isn't going to help, either. I intend to go back to Troy Hunt's article that you linked to. I'm going to start a new project and intend to write some APIs as a part of it. This editorial will help guide my architectural decisions.
Kindest Regards, Rod Connect with me on LinkedIn.