I've always been curious whether someone will succeed in using the same development strategy as Jane Street, namely using a non-C++ language as their primary language. I suspect OCaml may have been a very good choice back in the early 2000's simply because C++ was a much different language and there weren't many options for other languages. Building up an ecosystem was not a bad plan because most languages did not have much of an ecosystem anyways. Nowadays ecosystems are a lot more developed. But on the flip side, that could mean you could stand to use a language like Rust that has an ecosystem and interoperability with C++. I know Tsuru Capital uses Rust but I'm not familiar with any other firms.

It also could be that Jane Street succeeded regardless or even despite OCaml. At the end of the day OCaml isn't going to ensure that your trading strategies work. It's not going to suddenly create alpha. But I do suspect they've gotten serious hiring and marketing returns by using OCaml. And benefited the OCaml ecosystem as a byproduct, which is a pretty solid side-effect, even if side effects are not very functional :D