NodeJS is single-threaded, how then are large-scale projects built on it?

Question

Node.js

Good afternoon.
NodeJS is single-threaded, how then are large-scale projects built on it?
It is enough to add the code to the Authorization API:

for (let i = 0; i <= 1000000000; i++) {
      console.log(i);
    }

The example is contrived. But the same thing can happen with a long query to the database to get the user during authorization.
And no user will be able to log in.
And that's it, the whole service is unavailable.

Answer 1

> But the same thing can happen with a long query to the database to get the user during authorization.
Can not. The point is that waiting for a response from the database / network / disk, etc. does not require any action from the node and it can do other things at this time.
As a very simplified example, run it in your browser console setTimeout(() => console.log('готово'), 5000);. After 5 seconds, you will receive the message “done” in the console, but all this time you could use the site without any problems.