[IgorPartola]

Fair points. This solution works for me for now and I certainly know it is not limitless. The solution with setting selected_by is something I thought about and may implement at a later point. I also am a big fan of using GET_LOCK(), for locking rather than relying on MySQL/InnoDB's built-in locking since you have finer grained control over timeouts, etc.

I understand your concern about sharing this "dangerous" knowledge, but I disagree that the solution is to hide it in a deep dark place. Would you find it acceptable if I updated my post with a discussion on scalability and a link to TFA? That way a reader will get more information about building such systems, not less.

[molesy]

The point of the UPDATE .. SELECT if updated pattern is that it's a mark-and-sweep completely outside of a transaction. Avoid locking > lock as little as possible > lock as quickly as possible.

Your blog is your business, the Lorax speaks only for HN.. (hey is Internet Lorax a job?) It would of course be great to update your readers, it'd be cooler to update your application and tell everyone how it worked out! Then you've got a story you can actually submit again