Oh dear. The chattering classes are at it, talking about how the Twitter folks are dissing Ruby by announcing the replacement of some Ruby code with Scala code.
At the kinds of volumes that Twitter handles (and with what I assume is a somewhat scary growth curve), Twitter needs to improve concurrency—it needs an environment/language with low memory overhead, incredible performance, and super-efficient threading. I don't know if Scala fits that particular bill, but I know that current Ruby implementations don't. It isn't what Ruby's intended to be. So the move away is just sound thinking. (I suspect it also took some courage.) I applaud Alex and the team for this.
Instead of defending Ruby when it's clearly not an appropriate solution, let's think about things the other way around.
The good folks at Twitter started off with Ruby because they wanted to get something running quickly, and they wanted to experiment. And Ruby gave them that. And, what's more, Ruby saw them through at least two rounds of phenomenal growth. Could they have done it in another language? Sure. But I suspect Ruby, despite the occasional headache, helped them get where they are now.
And now they've reached the status of world-wide wunderkind, it's time to move on.
I for one wish them luck. I look forward to the day when our online store reaches the kind of size where we have to move away from Rails. I'll tweet the fact with a tear in my eye, while my yacht sails me off to the sunset.