Boost Cache helps some pages, hurts others? I'm working on fixing some performance issues of a Drupal 6 site. Very new to Drupal, been figuring things out as I go, so please bear with me here.

My client has a rather busy site and uses Boost cache. On pages where Boost cache is applicable -- their home page, reviews pages, etc,... -- it works great. Pages are fast, load testing shows that they can take whatever's thrown at them. I just discovered that with Boost enabled, pages that are not eligible for its caching, such as pages with polls that need to pull from the DB each time, they are significantly slower to load then when Boost is disabled entirely.

For instance, here are the Loader.io results of a page in question. The instances where it completed successfully were with Boost disabled, instances where it failed were with Boost enabled. Ignore that 100% error rate test that's second from the top, MySQL actually crashed after the previous test and I forgot to restart it before running again.



All I know for sure is that the errors are caused by MySQL. It appears that Boost adds database overhead, maybe it has to check for information about cached pages and then it has to do a second query to draw the page if it doesn't find the cached information? I'd love any insight anyone can provide!

Edit: Screenshot of Boost expiration settings
There is an option in boost that let you count the number of hits even of cached pages. That version hits your database on each page hit. It's fairly small, but it still loads all the modules as it has to go through the standard Drupal initialization.

Make sure you turn that off if it is on to ease the load on the DB.