I keep hearing that Rails can be scaled, but how does that explain the fact that Twitter had to switch off of Rails in order to scale?

Rails, as any tool, has its limits. When you're doing things at Twitter's scale, you need other tools.

I like the point on pushing work into a query instead of doing it in rails/ruby. That's not just a rails thing but helps on any framework/platform.

Github seems to have scaled fine on Rails.

Twitter has a many-faceted, hugely complex architecture that to my knowledge still includes Rails.

Not to mention that by the time that twitter needed to scale rails the framework itself was very different and a little less powerfull. That goes to ruby as well.

Well, Shopify is built in rails and its scaling extremely well. Rails can be scaled!

It seems like rails in 2.1 has improvements in garbage collection, definitely need to learn more to high scale rails.

Ruby 2.1 has a very important property: GC scales linearly with the amount of memory allocated.

Before 2.1 GC performance increased polynomially. So, for example, processing 10k rows from the table could take 10 seconds, and 100k would never finish.

With 2.1 everything I do actually finishes :)

Ruby 2.1 is a huge step forward. Surprised that more people aren't talking about it.

And I also like the fact that GC in 2.1 no longer takes 50-60% of execution time. Usually it's more like 30-40% now.

I think you mean ruby 2.1

I like the post. Is always great to learn new or different ways to solve the same challenge. Great tutorial.