We did not migrate the infrastructure during this maintenance period. Although we scheduled this maintenance with the expectation to perform the migration, we identified a blocking issue the day before.
We instead used the maintenance period to resolve that blocking issue. We successfully resolved the issue during the maintenance period and we will now schedule a future maintenance period to perform the migration.
The blocking issue was that one of our replicas between our current environment and the new environment got out of sync. This was due to a combination of an IP address change and an overly short retention period for the binary logs, which are what makes replication possible.
The IP address change created a connection error on the replica. By the time we identified and resolved it the necessary binary logs had been purged, leaving that replica permanently out of sync.
During the maintenance we stood up a new replica and ensured it was in sync. Separately, we also resolved the underlying issues that caused the out of sync issue by switching from IP-based addressing to DNS-based addressing and extending the retention period for binary logs in the new environment.