ASP.NET Core Web API code looks deceptively simple — a few attributes on a class and it works. The interview-relevant part, and the part that actually matters once an app is in production, is what's happening between a request landing on the server and your controller method running: which middleware touched it, where its dependencies came from, and what guarantees the framework is (and isn't) making along the way. This is a complete reference — work through it in order, or jump to the section you need from the sidebar.