We've now reached the point where the upgrade is possible. We have a brand new cluster running the newer version of PostgreSQL, all data has been copied, and we have tested the application on the new cluster to ensure compatibility. It is now time to switch the application stack to the new cluster and complete the upgrade transition.
PgBouncer will play a key role in this final step, and will ensure the application barely even notices the migration. This recipe will explain how the upgrade itself works, and the other steps we need to execute to ensure everything is fully synchronized.
