- OP mentioned performance. Erlang is terrible for - Haskell
- OP said non-esoteric.
- There's a significant ramp up before you learn to deal with the compiler and lifetimes.Erlang's CPU performance is not bad IME (though admittedly I can't think of anything I've implemented in both Erlang and Java to compare). But that's beside the point; you pick Erlang for networked and I/O bound tasks. Twitter mentioned running Heron on several hundred machines—at that scale, single-thread performance starts to matter less and Erlang's scaling efficiency closes the gap.
> Haskell
Haskell may have been esoteric in 2005, but it's hardly so anymore. (Also, I mention Mercury, and Haskell is the language you decide is too esoteric‽)
> Rust
So you're saying they wouldn't use it because they didn't know it. I suspect that's the real reason they chose Java—not because it is necessarily the best language suited for the task, but because it's the best of the languages Heron's developers knew.
Erlang is very slow when it comes to CPU bound tasks. It's nowhere near Java for tasks like this.