Instagram is presumably in the same position. Switching language is basically impossible once you have a certain amount of code. I'm sure they were aware of the performance issues with Python but they probably said "we'll worry about it later" when they were a small startup and now it's too late.
Hack is actually surprisingly pleasant, basically about the best language they could have made starting from PHP. (I know, that's damning with faint praise. But I actually mean this unironically. It has TypeScript vibes.)
IMHO Hack's best feature was native support for XHP... which (also unfortunately) isn't something PHP decided to take.
Last time I checked they're working on improving Python performance instead (yes I know they forked it into Cinder, but they're trying to upstream their optimizations [0]). Which is very similar to what we're doing at Shopify.
Of course 100% of Instagram isn't in Python, I'm certain there's lots of supporting services in C++ etc, but AFAIK the Instagram "frontend" is still largely a Python/Django app.
The joke is that if Meta thought that replacing all the Python code they have with something else was worth it, they'd have done it already.
"Worth it" depends on both how much performance improvement you get, and how hard it is to replace. Did you consider maybe the rewriting effort is so humongous that it is not worth doing despite large performance improvements? Thus making the joke not funny at all...
But that's some silly engineer tunnel vision, squeezing the very last bit of performance out of a system isn't a goal in itself. You just need it to be efficient enough that it cost you significantly less to run that the amount of revenue it brings you.
I can bet you that moving off Python must have been pitched dozens and dozens of time by Meta engineers, but deemed not worth it, because execution speed isn't the only important characteristic.
So yes, I find it hilarious when HN commenters suggests companies should rewrite all their software into whatever is seen as the most performant one.
Is the Instagram stack Python? I doubt it, but stranger things have happened
I suspect it is actually some derivative of Apache, or Nginx. Something sensible