It might make sense to put some compute intensive tasks in Go, or any other compiled language thats more efficient, but exec'ing and returning JSON isnt really a great idea.

If you were going to consider this seriously, then you should have the target app start once, listen for comands on some channel like a socket, and have it return information. JSON is probably a little too verbose for this kind of use-case as well, but it depends how efficient Ruby would be at unpacking alternative serialization formats.