Every job I've has has used different languages so I don't really understand the need to find a dev for a specific language. I went from network firmware in C to banking application servers in Scala and it took like 2 weeks to ramp up. Not a big deal. Now I write lower level networking stuff again in Go, which seems like its just worse than e.g. C-with-templates (and occasional classes) style C++ so I don't really understand why people like it.

I think it used to be common to just look for smart people and assume they can run with whatever stack. Wasn't that the point of abstract algorithm questions etc. (basically an IQ test)?