As commented https://tracker.moodle.org/browse/MDL-48006?focusedCommentId=319333&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-319333, the new autosave feature is adding a database write every time a user loads a page with an editor, to be more specific, 1 more db write for each editor.

I don't have numbers, but it seems that it could be a problem on sites with many concurrent users performing synchronized activities (talking with Damyon he discarded mod_quiz as it is using a different system) as the db table would remain locked.

The feature is awesome, but IMO we should ensure that this will not be a problem once 2.8 is released, our performance tests would not be useful here as they are not testing JS code; if it may be a problem we should think of a way to avoid this db write (Damyon commented about it https://tracker.moodle.org/browse/MDL-48006?focusedCommentId=319338&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-319338) or at least, a way to disable the autosave feature to see how it affects to protect users if the performance impact is too big. The current code is doing this first db write even if the autosave feature is set to refresh every 0 seconds.