Not all $technologies are equally easy to come up to speed on. Similar domain, different language? Mostly easy. Completely different domain, same language? Prob

Not all $technologies are equally easy to come up to speed on. Similar domain, different language? Mostly easy. Completely different domain, same language? Probably hard. Both? Really hard. You wouldn't hire a senior javascript programmer to write CUDA c code, and vice versa. You'd happily hire someone who hadn't ever written web apps in c# but was a senior java person building web apps...