They probably were doing fetch requests for the dashboard client side. I wonder if they had the entire db url stored as a next_public_db_url. If that’s really irresponsible, and pretty easy to catch in development, at least for the pages router stuff. Maybe a little less so obvious for ssr pages.
I haven’t tried a lot of the new app_router, maybe there’s a lot more mixing of client and server side stuff there. Regardless, you should be auditing your environmental variables!
Some frameworks automatically detect this and fail to build if you do it, but apparently not all of them.