Why does the dev server take 700ms to serve app.js?

I notice that the dev server takes 700ms to serve app.js. Of this 200ms is “waiting” and 400ms is “content download”. I wonder why that is? Shouldn’t it be a quick local retrieval taking a few hundred milliseconds at the most?

Also, for testing purposes, I want to set app.js (and other static assets) to be cacheable. Right now, it is served with a header of max-age=0. Where/how can I change the cache settings for files served by the dev server?

700ms looks preaty wired.

What operating system, JS runtime and web browser do You use?

Also what is Your website size? (Is it assets heavy?)

Last but not least. Are some performance profiling options enabled in Your web browser?