Thanks for sharing, ocaml is an interesting language which I think has it's pros and cons

Pros:

1. High Performance with solid safety guarantees

2. Greatly improve developer productivity through advanced type features

3. Exceptional reliability for mission-critical systems

while I also have some concerns about it as well

Cons:

1. Steep learning curve with significant paradigm friction

2. Constrained ecosystem and limited career opportunities

I know like Kevin Kelly is a fan of such kind language like Lisp he mentioned in his book, out of control, which is my favorite one, but still, I dont like learning another new languages, yes, I am very lazy!

For parallel programming, what's OS-level difference compared to languages like Python or modern C++?

Domain.spawn (fun _ -> print_endline "I ran in parallel")

Anyway, love the simplicity of this expression!

At the OS level, OCaml 5+ and C++ can spawn OS threads. Python can't.

Are there any production quality apps or application libraries for OCaml? I'm not sure in what area the OCAML ecosystem is well developed?

Many. See https://ocaml.org/industrial-users

A high-quality library to try out is the Dream web framework: https://aantron.github.io/dream/

Tx!