Websites crashing under unusually high load typically has more to do with a lack of caching or undersized db than choice of backend.

This has been my experience as well. Rails can do a lot, but it also allows you to develop junk. Most sites built in Ruby end up in the latter category, especially if built by a team that doesn’t use basic software architecture patterns.

HNs hug of death does not apply to Rails only

Well actually, if they had used Next.js deployed via Vercel or something similar, it would have been statically cached on a CDN and prevents issues like this. But because they want to use older technology that's more difficult to cache and proxy, this happens.

God, this reminds me of the worst sort of discussions I’ve had with people who don’t understand the technologies they are working with. I’m sorry for being so negative, but “older technology that's more difficult to cache and proxy” is just nonsense.

It's nonsense and worse: hype. I recently went through a bunch of Vercel apps and compared them to some of my favorite Rails/Django apps. The best performing Vercel apps were on par at best.

Can you point us to your Vercel apps and what kind of traffic you're dealing with?

I rescaled my VPS. Let me know if you still experience issues.

Out of curiosity, what kind of request/second are you seeing and what was your before/after VPS cores? Is it built with rails?

I don’t measure req/sec here, but at one point, I had 2.8k visitors in an hour. Before rescaling, it was running on Hetzner’s CPX11—2 vCPU cores shared with a few other Rails apps. (I didn’t expect it to go viral at all)

I forgot to mention that yes, it's built with Rails. https://weuserails.com/ruby-on-rails-websites/we-use-rails