It's great that you have such a powerful machine. As a software (web) dev I can tell you that it means nothing (except for you showing off ;). I do agree though that Airbnb's web app ("website") is indeed *ridiculously* slow.
That's why I landed on this thread, of course.
The performance issue is fully on the server side. No it's not client-side JS (they don't have much of it) and that type of performance slowdown "feels" very different.
The Airbnb web app app is built with Rails which I'm a big fan of. While Ruby is a "slow" language, it is still quite popular and used by fast sites. The fact that it's slower than other (compiled) languages such as Go or Crystal really just means that the devs and devops folks just have to do a bit more work to make it feel as fast as services like Facebook, Google, Github (also built with Rails), etc. These things include caching and other optimizations of that kind. And also having faster and just more quantity of web servers, horizontally scaled and load balanced (which I'm sure they have at this scale, but maybe not enough of? Not sure).
Anyway, I also am in a bit of shock at how slow this app is. I know it's not a simple codebase, but surely there must be so many easy wins. I don't want ot make it sound like performance optimizations are easy. They are actually some of the hardest problems to solve, especially with such a busy/popular app. But they have the money and resources.
I assume their team is quite aware of the situation and are on it. I just want to +1 that it would be nice for it to feel at least "normal" in terms of performance. Don't need it to be blazing fast imho.
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After writing this I just did some quick DevTools based analysis on their CALENDAR page. And at first glass it seems quite unoptimized. Notes in the screenshot: https://d.pr/i/2NvgXV