As clarified in the documentation Predefined App Engine roles, the below roles are the ones that can visualize the configs from App Engine:
- App Engine Admin
- App Engine Service Admin
- App Engine Deployer
- App Engine Viewer
- App Engine Code Viewer
Outside of the users with one of the above roles, no one should have access to your config files, which includes your config.json
with your secrets.
Since this is a security matter, I think adding encryption is always a good idea. This way, you will add an additional layer of security to your application - something that is always good.
In case you decide to go with encryption, I would recommend you to check this post here, where some encryptions and options of how to do it are described and that I believe would help you.
Let me know if the information helped you!