Given all the previous factors and notions, certain UI design principles can now be abstracted and understood.

Firstly, speed is important to users. So, if no other optimization of your application can be done, make sure your users have the possibility to start using the application even before the initial page has finished rendering. This means getting to the First Meaningful Paint (FMP) of the page as quickly as possible in order to reduce the time it takes to get to the "time to interactive," which is the first moment when a user can start to interact with the application. One basic technique that can help you load the page's "above the fold" content before anything else is to place all blocking JavaScript at the end of the body of the page. Also, certain parts of the page can be cached for faster rendering or can be loaded in the browser through AJAX requests that are triggered with a periodical timer for example. Finally, HTTP/2's server push feature...