Imports are asynchronous, but they are still eager, and still run before the code in the module. Furthermore, the bodies of modules will still execute in the order you import them in. Basically all being Asynchronous means is that the interpreter is allowed to use multiple threads to load and parse the referenced modules "out of order", but will still execute them in order.

Thus your whole static import tree will be resolved before the first request comes in, assuming you start the server listening in the body of your main module. If you start it in the body of an imported module, and have other later imports that have start-up task side effects, then yeah you might have some requests come in before those later side effects happen, but why would you structure your code like that? The modules approach generally favors not having side effects in from importing modules, except the program's top level module of course.

Now dynamic imports are fully asynchronous, returning a promise. But even then you can structure your code to ensure they are loaded before your start accepting connections, or you can structure dynamic imports to be lazy and on-demand. This is not much different from CJS where you can also structure any dynamic imports to be either lazy or eager. The main difference is that with modules you need to deal with a promise while with CJS's require you don't.