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GitHub User: Sephi-Chan
Can you please add in the show notes some of the libraries to process images client-side. It would be helpful! :)
The memoization is per-request based. It's good when you want to call the same (heavy) methods many times in a request lifetime (for instance, current_user).
I'm surprised you didn't show the russian dolls technique as exposed by 37signals few months ago (http://37signals.com/svn/posts/3113-how-key-based-cache-expiration-works).
It's a great video anyway, as always. ;)