7. Why must I reenter the database password/AUTH-token at a cluster restart?

When the data store is set to default, then the connection authorization password (which is the AUTH-Token) is stored directly on the Airflow cluster in the default data store, which is also on the cluster. That means that when you restart the cluster, you must re-add the password (AUTH-Token) because it would be erased since the database gets deleted when the cluster is offline.