I'm actually really glad to hear it. Though, I wonder about the "rails doesn't scale" mantra, is that really more for active record? In your experience is active record the biggest out of the box bottleneck?
The "rails doesn't scale" mantra was discredited 5 years ago, when people realised that it scales exactly the same way as PHP. Remember, scalability != performance.
We handle a lot less traffic than Shopify (~15-20 million reqs a day) but ActiveRecord isn't a bottleneck and I wouldn't expect to to be [...unless you are talking about something other than the performance of AR as a body of code?]
Instead of "Rails doesn't scale" we should say "Rails runs on Ruby which means that it will consume significantly more CPU and more memory* compared to something else"
In my case, 1 extra server (my estimate) was a small price to
pay for developer happiness.
The issue they have doesn't seem to be scaling, in that RoR is scaling linearly. But if you have hundreds of machines, raw performance saves real money, which means RoR is maybe not ideal for massive deployments and the JVM languages give you more performance on the same hardware. Though unless you're working on a top 50 site I wouldn't worry so much.
From what I read, "rails doesn't scale" is really a misnomer, because there are number of things that can be done to scale rails. I think Haiping Zhao of Facebook made it clear, that it's really just an efficiency problem. Bottom line, rails requires more computing power than jvm for sites like twitter. Which are only a handle of sites.
That seems to be the case. The view/controller layers can be scaled via more machines. Its the database layer that requires synchronization. Thats a universal problem, though.