architecture for Blue/Green deployments

My organization is moving into the AWS cloud, and with some other projects using MongoDB, ElasticSearch and a web application framework that is not Django, we've had no problem.

I'm our "Systems/Applications Architect", and some years ago I helped choose Django over some other solutions.   I stand by that as correct for us, but our Cloud guys want to know how to do Blue/Green deployments, and the more I look at it the less happy I am.

Here's the problem:

• Django's ORM has long shielded developers from simple SQL problems like "SELECT * FROM fubar ..." and "INSERT INTO fubar VALUES (...)" sorts of problems.
• However, if an existing "Blue" deployment knows about a column, it will try to retrieve it:
• fubar = Fubar.objects.get(name='Samwise') 
• If a new "Green" deployment is coming up, and we want to wait until Selenium testing has passed, we have the problem of migrations

I really don't see any simple way around a new database cluster/instance when we bring up a new cluster, with something like this:

• Mark the live database as "in maintenance mode".    The application now will not write to the database, but we can also make that user's access read/only to preserve this.
• Take a snapshot
• Restore the snapshot to build the new database instance/cluster.
• Make the new database as "live", e.g. clear "maintenance mode".   If t he webapp user is read-only, they are restored to full read/write permissions.
• Run migrations in production
• Bring up new auto-scaling group

Of course, some things that Django does really help:

• The database migration is first tested by the test process, which runs migrations
• The unit tests have succeeded before we try to do this migration.

Does anyone have experience/cloud operations design with doing Bluegreen deployments with Django?

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