Without getting too involved with details (I was working for a certain company that doesn't like people talking in detail about anything I did there), I had a program that routinely started other processes. I was required to use Java or Clojure, and we had a sort of quasi-RPC thing that would spawn process on the shell, get a result, and return that result as a string. This application wasn't super performance-oriented, but it was enough to where a 5 second start time was untenable.