This section only applies to JSS sites that use Deploy and Optimize.
When a static site is generated for a JSS site, JSON files are created that represent the calls that are made to the Layout Service. These files would be used using client-side routing (i.e. SPA navigation). This type of navigation is not currently supported for Nextjs apps, so these files are not needed.
These JSON files are generated in the following path:
You probably will want to add a step to your build process to delete these JSON files after they are generated because they contain a description of any personalization used on your site. If a visitor knows where to look, the visitor would be able to use these files to discover content that personalization would normally hide.