According to noted internet pundit Arrington twitter has made the call to rewrite and move off ruby on rails. Not really a shock, rails is fundamentally not going to scale up past a certain point.
The uncharitable part of me (and the part that is confident nobody reads this blog) thinks that the vast majority of rails developers have never been around the kind of scale we’re talking about when we say rails doesn’t scale. Especially when I see something like this:
I love that items 2, 4 and 5 are REALLY REALLY hard.
More likely though those developers haven’t faced an app that is particularly hard to scale. I think the issue is less “does my framework scale” and more “is my application going to be hard to scale”.
Twitter is a great example of the kind of app that is very hard to scale, regardless of the platform. Rails is probably not the culprit here, but I doubt it is helping at all. In fact, at this point I would suspect twitter will do what everyone ends up doing when this happens: php frontend talking to a web service driven by java (or c). Because it turns out when the problems get real hard you don’t want a scripting language to handle them.
Rails isn’t bad, but it is isn’t “easy” to scale, except in cases where the application is easy to scale (content). Rails is designed by small, custom app developers for small developers. It provides one major benefit: it makes it faster to develop a certain class of applications. Thats it. So if time is money (you are a small dev shop) rails will make you money. Otherwise rails give you very little. I don’t think it would be a bad choice for most apps, but I don’t think its the panacea many rails advocates would claim.