Aaron Patterson (tenderlove) gave a presentation where he said he wanted to refactor rack to make it more simple. He said Rails 3 had a lot more depth in the stack and it was making it slower. (when i start up an old rails 2 app i can't believe how fast it is). I don't think that is in Rails 4 though. I guess that is a separate project.
Also deprecating vendor/plugins means Heroku will have to change the way they deploy. You can notice that by the deprecation messages when you start a heroku console.
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Aaron Patterson (tenderlove) gave a presentation where he said he wanted to refactor rack to make it more simple. He said Rails 3 had a lot more depth in the stack and it was making it slower. (when i start up an old rails 2 app i can't believe how fast it is). I don't think that is in Rails 4 though. I guess that is a separate project.
Also deprecating vendor/plugins means Heroku will have to change the way they deploy. You can notice that by the deprecation messages when you start a heroku console.