I have a custom domain (travelbox.id) that connected to Firebase Hosting already. I also have an App Engine application to serve as my API. I want to host the App Engine application on api-dev.travelbox.id. I mapped the custom domain to App Engine following this docs but domain connection to Firebase Hosting stop working. If you access api-dev.travelbox.id it is connected to App Engine. But if you access travelbox.id it doesn't connected to Firebase Hosting.
Is that impossible to achieve what I want?
I found the solution myself, here you go!
On the fourth step in this docs, i didn't add A records, just add AAAA records. Suprisingly, it works! :D