non-blocking node.js express web server [duplicate]

The async keyword, and promises in general, don't make synchronous code asynchronous, slow running code fast, or blocking code non-blocking.

async just makes the function return a promise and provides (with the await keyword) a mechanism to interact with other promises as if there were synchronous.

Your function starts a loop, and then just goes around and around.

It doesn't get to the end of the function, which would end the function and resolve the promise it returned.

It doesn't reach an await keyword and pause while it waits for the awaited promise to be resolved.

It just goes around and around.

If you were actually doing something in the loop which was computationally expensive and you wanted to push off into the background, then you could use a Node.js Worker Thread or a browser-based Web Worker to do it.