I'm curious too how much of each of these is still built on Rails, and how much has been tweaked, tuned and rewritten to be 'inspired' by Rails, but no longer Rails.
Good question. I would say it varies, but after all they are mostly likely not changing things dramatically, at least thats what you get from watching talks from both companies[1].
I've browsed this discussion and I must miss something?
You seem to imply Ruby's/Rails' speed matter?
Usually, the DB is the limiting factor in most web applications, few should need to execute more than a few milliseconds of (even) Ruby per page load. That is why people use scripting languages, after all.
Shouldn't this slowdown be a problem in the ORM for this version? I'd look at access patterns for normal requests for the new Rails version and the old. How has the SQL changed?
Sure, Twitter is different since that probably is processor bound.
(Since RoR is a popular framework with lots of eyes, there shouldn't be something simple with e.g. configuring the web server, locking etc.)
