They use Varnish for pages, and two CDNs (Fastly and Cloudinary) for everything else. Varnish is insanely fast, on my servers I can get page load times down to 1/3 of a second with it.
Pretty annoying, though, that they hijack users' familiarity with the red dot to deliver the useless notification that "You are not logged in on this device".
It's essentially an ad that gets you to click it by making you think you are somehow logged in on a site you don't have an account on. I emailed them about this because I think it's an awful pattern, and did get a response but not one that indicated they understood the problem with this deceptive marketing technique. It makes me avoid clicking links to dev.to.
Noticed they start loading content as soon as you hover your mouse over a link. Wonder what their server loads are like because of this.
On my mobile so I can’t poke around... what did they do to make page loads so speedy? Even images seem to be quick.
They preload everything. They preload a post when you mouse over it, so it's mostly/completely down by the time you click. They also preload the current most popular posts, things like that.
Looks like all their server-side stuff is coming from Heroku.