It turns out that Wordpress 1.5 isn’t as efficient on your SQL server as you’d hope. In a message to the wordpress-hackers mailing list, Sencer writes:

I am trying out WP1.5 and looking at the query-log of mysql for a page-request that only displays a list of 10 entries. Some queries are identical/duplicates, so the code could be easily rewritten to drop these queries. This is only a suggestion. Maybe one of the devs that is familiar with the WP codebase wants to look into this.

Here is a list of the queries as they are made during execution: www.sencer.de/code/wp/qlog.txt And here is a sorted list: www.sencer.de/code/wp/qsort.txt

If you look at his findings, there are almost two dozen calls to the wp_users table that could be rolled into one query, as well as some 100% duplicate queries. Probably the best solution would be to wrap everything in a query cache, and optimize the code which queries the users table. As a developer, always remember to profile production code, especially web code!