> So, if that isn't the competitive advantage, why go for it in the first place? At least blue collar languages have much, much larger pools of competent progra

> So, if that isn't the competitive advantage, why go for it in the first place? At least blue collar languages have much, much larger pools of competent programmers to select from, which is an objective, convenient upside any manager can understand. I think its like Haskell, Rust, Go, Erlang, etc. These languages are extremely useful in the microcosm of places where they excel. Rust when you absolutely need to insure memory safety, Go when you need near-C speeds but a simple to use concurrency system, Haskell for rigid typing, Erlang for high availability, etc. The problem is the dead average developer looks at these, and sees these high flying companies doing cool things in it, and then decides "wow I should write everything in this - it's the future!" Scala is the same way. It's not objectively better than a modern java in any way which might be taken as fighting words. But foregoing a lot of developer history you gain the power to reason about a very, very small subset of programming easier at the cost of speed, time, etc. For a company like a twitter with a very specific use case for this it made sense. Especially since at the time twitter switch from RoR to Scala, Python and it's concurrency platform didn't exist. However, I would speculate if they switched today they would've almost certainly gone to Python which would have been a much less "cool" switch and probably not even made the news cycle.