What do big projects use for asynchronous programming?

Question

Asynchronous programming

Consider the example of VK, for normal operation and writing normal asynchronous code, you need suitable tools. However, VK does not use node.js or socket.io, I did not find signs of their presence, most likely they have their own not sockets but workers in their pseudo PHP language, although PHP was not created for this.
What and why do they use self-written tools?
After all, it would be possible to use without problems what is already there, only adding a little for yourself.