We run Viewtracker on large instances with up to a million pages. We can confirm that Viewtracker does not degrade the performance or stability of Confluence.
However, depending on the Confluence configuration, the amount of content and simultaneous user interactions, a performance loss can never be completely ruled out. We recommend making the following two settings if you run into performance issues:
Dark feature "Batch Inserting"
Enable the batch inserting as described on this page.
Set the "Cache statistics" toggle to active on the setting page, as described here. This will delay the refresh of the metrics displayed in the different reports, which helps to reduce the load of requests.