Well, it is hard to get a true picture without some probably paid data, but Scala has been around for longer (especially if we only look at the time when the language was reasonable well known), and I know plenty of companies that have significant Scala code bases even from the top of my head. Rust, not much. Of course I could be dead wrong, but I think as of now Rust has more hype than actual code written in it (but it is not baseless hype, imo the language actually lives up to it so its usage will likely grow faster than Scala’s)