The built-in Django libraries for Django on App Engine are severely outdated. I have new guides that just vendor in recent version:

https://cloud.google.com/python/django/appengine

However there are a lot of tricky issues with Django on App Engine so I would also look into Djangae:

https://github.com/potatolondon/djangae

As far as Kubernetes, the OP and I had some independent discovery and started working on similar material at the same time. I also have some Django/Kubernetes content, both CloudSQL (MySQL) and Postgres in Kubernetes:

https://cloud.google.com/python/django/container-engine (CloudSQL)

https://medium.com/google-cloud/deploying-django-postgres-re... (Postgres)

My biggest reason for running the database in Kubernetes is a) CloudSQL doesn't currently support Postgres and b) it's interesting. Seems like OP had similar motivations.

Obvious disclosure: I work for GCP.