You want to migrate an on-premises mission-critical PostgreSQL database to Cloud SQL.

Take nightly snapshots of the primary database instance, and restore them in a secondary zone.

Build a change data capture (CDC) pipeline to read transactions from the primary instance, and replicate them to a secondary instance.

Create a read replica in another region, and promote the read replica if a failure occurs.

Enable high availability (HA) for the database to make it regional.