Drupal Performance Tip: Block Visibility | Lullabot

Drupal's default behaviour is to render every single block on your site that's assigned to any region on every single page view, regardless of whether the region's content is actually being visibly printed out or not.

If you're doing a bunch of complex queries in those feature blocks, and you're not hiding the block by one of the following:

* Setting the block's visibility settings (on the block's configuration form) to not show up on pages that do not have the region it's assigned to printed. For example, setting any blocks assigned to the Feature A region to only show up on the <front> page.
* Hiding the visibility of the block by some other means; for example, by limiting it to a role using the checkboxes on the block configuration form (or content types in Drupal 7), or installing a contributed module that implements hook_db_rewrite_sql() on the block list.


...then your server is probably melting. :P