Atlassian products seem to use a really great code-splitting-like tech: 4MB js bundles are dynamically generated from a list of which modules should be included in the bundle which is dynamically generated by some other js on the page. So you're essentially guaranteed to get the same modules into your cache a dozen times in slightly different 4MB js bundles.

Are you referring to https://github.com/atlassian-labs/react-resource-router ?

I'm not sure what the tech is called other than the reason I spend multiple hours a week waiting for jira and confluence to load pages with like 300 words on them