Ask HN: If you were building a HFT system today, what language would you use?

Golang. For performance with support for coroutines and garbage collection. The other choice would be C++ since tooling has improved greatly since 2003.

Thanks -- yeah, Golang GC seems very performant.

Ada/SPARK for anything that modifies a currency value, because safety is worth a few microseconds overhead.

Lisp

Lisp seems great for describing certain classes of trading algorithm, but what about the underlying platform?

Underlying platform? Since it does sockets nicely no need for more.

Yeah -- I can see what you're getting at.

Perhaps Common Lisp? But why and how?

Why not? It is at least as fast as Java has all the networking tools. Yes common lisp.