In response to Augustin, I don't think there is any way around the complete invalidation of cached pages when a node is added, since a single node may be displayed in part or whole on any or all of the site pages. Seems like object-level caching needs to be the next step: http://drupal.org/node/74020 and having a sensible API would make it easier for modules to appropriately invalidate the cache, set a time limit on the cache, or prevent objects from ever being cached.
Date: Tue, 1 Aug 2006 22:31:14 +0800 From: "Augustin (Beginner)" <drupal.beginner@wechange.org> Subject: [development] Cpu usage: something is very wrong (caching).
I just reviewed the Caching, Caching, Caching thread, but I didn't see that it addressed an issue that I recently learned about and that I find somewhat shocking: the whole {cache} is being emptied whenever a node is created or edited, meaning that even a medium-traffic website with many nodes but only one or two added every day will see a very high cpu usage, because the 100s of nodes will always be purged from {cache} before Drupal has a chance to serve the cached page to a second visitor.
This approach defeats the whole caching purpose.