Well, github, just to name one:). Also shopify, digital ocean, stripe. I also worked on a large ruby app that was faster than another large Java app. Keep is mind that all these platforms handle a great deal of requests at any given time, so we're not talking simple web apps.

In my experience bad software design, bad DB design and bad developers are the major cause for performance issues, you rarely get to that level of polish with your app that the difference between different languages really matters.

At micro-bench level PHP always beats ruby pr python, but most apps have performance issues without ever getting to that level.

My funnies experience was with a java team that where baffled why their app is slow. I told them it looks like they have a huge bottleneck on the DB, their answer: "Yeah but it's java, it should be fast"

github is terribly slow... or maybe it's just me?

It's usually fast for me with the occasional slow down.

From experience (did some code contributions to gitlab) when you work a lot with the filesystem, as is the case for platforms hosting git repos, you will have performance issues related to that, regardless of the programming language.

we host gitlab at my company for internal use, just switching from SSDs to HDDs made a big difference in terms of response time for big actions like opening a merge request, etc

I'm sure there are apps in the wild that get to that level of optimization where you need to decide on a different language. But what I've usually seen is you just slice that part out into a service and only rewrite that part.

I think stripe and others are basically doing this if they do hit the limits of ruby in very performance intensive workloads.

It's rarely application code itself that leads to something being slow(though bad code can, of course, be slow).

It's usually database calls, external API's etc..

For example, JIRA is as slow as a dehydrated donkey because its database schemas are exceptionally awful.