I wish I had numbers, but in my experience it’s far better than you’d expect. Basically take the length of a REST call you’d have to make anyway and add a few milliseconds for the rendering.
How about you try it and see?
Both, I guess.
And I have written a library that does the full SSL handshake/upgrade cycle off of tcp sockets, and managed my own private CA, so I'm not a total idiot.
Also the latency of your connection matters.
HTMX is fine with showing loading icons are the like if needed, but yah, connection latency is going to have an effect.
FFS, people, learn to write proper software that does everything locally!
As opposed to the >2MB initial page loads that have become so common with heavy React SPAs in exchange for the theoretical benefits of avoiding more page loads for further interactions.
Software that doesn't need the internet for its function shouldn't connect to the internet. Software that does need the internet should be able to operate under adverse network conditions.
The Voyager probes are 160 AU away, far past Pluto, with a roundtrip latency of 37 hours. The radio transmitter onboard is only about 10x more powerful than a cell phone. The hardware has been in the cold vacuum and hard radiation of space for four and half decades. In spite of this, NASA maintains active two-way communication with it today, and continues to receive scientific telemety data of the outer solar system.
I don't expect web devs to design for deep space, but the core functionality of a website should still work for a rural user with a spotty satellite uplink. Don't do go loading JavaScript or other resource calls until the basics are received. I still remember the days of Facebook being fully functional on a 2G cellular connection, using little or nothing more than static HTML and CSS (and that was before the magic tricks HTML5 can do).
As an example, you may have an HTML table on your page that you want to insert a new row for some reason on let's say a button click. You place some attributes that htmx understands on your button that will call for the TR HTML chunk from the server. You can imagine replacing all the rows for a paging click etc.
Again check out the example for cool stuff.