mikhaill - 4:26 am on Mar 23, 2008 (gmt 0)

You should also worry about how many SQL calls your hosting allows (assuming you're not running your own dedicated DB). The problem is really not WP scalings it's the DB that it runs on.

As many people have already mentioned caching is essential. You may want to implement some custom caching, especially if you're page content doesn't change much once it's entered. It may make sense to cache the entire page and rewrite it every X hours with a newer copy. I haven't really using any of the plugins that are used for scaling WP but having thought about the problem, there are a few places where its fairly simple to modify the DB access layer to implement better caching.