The Boost module creates static copies of a website's webpages in an attempt to improve the website's perceived performance for website visitors.
Due to both of these reasons, while Boost is perfectly acceptable for use on single-server websites that don't use a network-attached file system, Acquia does not recommend using it with Acquia Cloud-hosted websites.
Anonymous website visitors are served static pages instead of Drupal having to access its database to create a webpage from scratch, which can be noticeably faster for website visitors depending on the complexity of the webpage.
This technique is effective on traditional single-server websites. However, because of Acquia Cloud's infrastructure, any improvement Boost can offer is superseded by Varnish caching. Comparing the two methods, Boost saves its static webpages as files; Varnish serves its cache from memory on load balancers. Because of this, Varnish can serve webpages much faster to website visitors.
Also, with Boost enabled, the increased interaction with the distributed file system on Acquia Cloud can negatively impact the server. Boost uses file system reads and writes with great frequency when setting and accessing the page cache, which can cause the server to experience heightened CPU usage.