It's frustrating seeing examples of MySQL being slow as an example of why you should use NoSQL. If you have an invested interest in comparing two technologies that are already apples to oranges, the least you can do is optimize both. If you can't do it, don't share it.
This came out of a talk on Cassandra. "MySQL" is not on the slide, but it was mentioned in reference to MySQL:
SELECT * FROM tweets WHERE user_id IN (SELECT follower FROM followers WHERE user_id = ?) order by time_tweeted DESC LIMIT 40;
Let me simulate that for you:
CREATE TABLE `tweets` ( `id` int(11) NOT NULL AUTO_INCREMENT, `user_id` int(11) NOT NULL, `info` text, `time_tweeted` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP, PRIMARY KEY (`id`), INDEX (time_tweeted), INDEX (user_id) ) …[Read more]