The blog was getting timeouts when I posted or scheduled an article. After much gnashing of teeth, I discovered the culprit was an incredibly ill-mannered WordPress plugin called Blackbird Pie. This seemingly innocuous plugin displays a tweet in a post, but does so by insane amounts of database queries.
From the WordPress forums
It turns out this plugin is returning all registered users on the site, looping through them and retrieving the meta data for each using a separate query for each and storing this on every page load, simply to check and see if there’s a stored twitter handle available for the post author of the current post in the loop.
It’s really kind of appalling that a plugin can be that sloppily written with no apparent concern for overhead and processing time.