PostgreSQL Upgrade (v9.5 to v12) with Django 2.0

Dear Community,

We are in the process of planning a PostgreSQL upgrade and would greatly
appreciate any insights, best practices, or lessons learned from your
experiences.

Current Setup:
- PostgreSQL version: 9.5
- Django version: 2.0
- Database size: ~3 TB
- One Master 4 Replicas(Streaming Replication)

We are taking a phased approach to this upgrade. In Phase 1, our goal is to
upgrade PostgreSQL from v9.5 to v12, ensuring compatibility with our
current Django 2.0 application.

As part of this, I would like to understand:

- What is the highest PostgreSQL version reliably supported with Django 2.0?
- What upgrade strategies or methods have worked well for you in similar
environments?
- Any gotchas or performance considerations to keep in mind with large
databases during such upgrades?

Your recommendations and experiences will be extremely valuable in helping
us plan and execute this upgrade smoothly.

Thank you in advance for your support!