Python is technically multithreaded, but the GIL means only one thread can execute interpreter code at a time. If you use libraries written in C/C++, the library code can run in multiple threads simultaneously if they release the GIL.

I vaguely recall Node used to run multiple threads under the hood for disk I/O, but it might use kqueue/epoll these days.

Node is essentially a single-threaded API to a very capable multithreaded engine.

https://youtu.be/ztspvPYybIY