A safe MySQL upgrade that wasn't so safe

A seemingly routine MySQL upgrade exposed a silent data integrity failure: an AUTO_INCREMENT column was assigned different IDs on the replica than on the source, and MySQL’s mixed binlog mode replicated some related updates differently across tables. For CIOs and technology leaders, the key lesson is that database upgrades and schema changes can create hidden corruption risks that directly threaten application correctness, customer trust, and incident response costs even when the cutover appears successful. IT organizations should treat replication behavior, binlog format, and post-migration data validation as critical controls in change management, not implementation details.