Both; array languages are really easy to learn when you have someone teaching you, so you can train newbies in a couple of weeks. I think 'RodgerTheGreat has a

Both; array languages are really easy to learn when you have someone teaching you, so you can train newbies in a couple of weeks. I think 'RodgerTheGreat has a few anecdotes you can find using HN search on that. But it definitely helps to know it beforehand. APL/J/K job postings are pretty common, although less common than C or Rust postings. Just keep an eye out and you'll see one eventually (and if you do your stuff in public, you'll probably get an offer from one of the usual suspects).