[sweeneyrod]

There are significantly more devs than that (the total is also over 900, that's from 2018).

It depends what you mean by "optimizing their engineering stack". They certainly do put a lot of effort into tooling, by necessity since historically there hasn't been much available for OCaml. For an example of stuff going beyond the open source work to make OCaml usable for large projects, see https://blog.janestreet.com/putting-the-i-back-in-ide-toward...

Obviously there is a lot of infrastructure that you need at a FAANG and not at a company with a few hundred devs. But any trading company that doesn't want to pull a Knight Capital needs to make sure their software is correct and reliable (probably to a greater extent than most of a FAANG).