I'd argue that Java or C# would have worked out just fine for Twitch. There was a recent post on Twitch's early architecture, and it seems they started out with

I'd argue that Java or C# would have worked out just fine for Twitch. There was a recent post on Twitch's early architecture, and it seems they started out with Ruby. Unsurprisingly, they had to switch from it once they needed performance (similar story happened with Twitter).