[troupo]

> but do you think PHP was a good option, or was it a "fitting a square peg into a round hole" situation?

Facebook was founded in 2004. Whatever fancy tech you're thinking that would fit the round hole, it didn't exist then. They also never thought it would serve a couple billion of users one day, so they built it in whatever they had and knew at the time.

Same for Instagram and Python (they started with Django).

[zitterbewegung]

How they have used Instagram with Django is that they have replaced pieces of Django over time with custom parts which is a benefit of the design of Django.