Debug mode may be used to diagnose performance problems with frontend pages.
Debug mode can be activated for individual users who belong to a user group:
When Debug mode is enabled for a user group, its users will see a Debug button in the upper right corner of the browser window.
Clicking on the Debug button opens a new window below the page contents which contains the SQL statistics of the page, along with a list of API calls and individual SQL statements:
In case of performance problems with the page, this window may be used to search for the root cause of the problem.