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The query annotations show up as a mysql comment next to the query. I don't know if we have any automatic indexing of the annotations themselves.

We try to stick to ruby/rails since so many people are comfortable in that environment. We try to balance the desire to break pieces out with the fact that it lowers the number of devs qualified to work on it.

There is a little more info on query comments here: http://samlambert.com/posts/the-power-of-query-comments/

Looks like they're using https://github.com/basecamp/marginalia for the tagging.