We noticed that in production, this gives the best performance for two reasons:
bundling all widgets together offers
the best compression (and thus
overall amount of bandwidth needed)
performing many different requests incurs a relatively large performance hit, it's better to perform it once and only have the roundtrip once.
The latter is what you're seeing in your graph: you're getting all 304's, which are pure requests without any payload (your webbrowser is asking the server if there's a new version. There isn't, so it's using it's local version).
In production, you're going to see two things:
from 5.16 on, all custom widgets are
bundled, so only one request for custom widgets. Due to compression this actually doesn't really eat up that much performance
we've improved the caching configuration vastly. You shouldn't even have to perform a 304 request if you haven't redeployed.
All in all, the first time you visit a Mendix app, it'll be slightly slower, but after that all pages and reloads will be extremely fast.