A company manages infrastructure with AWS CloudFormation for dev, pre-prod, and production. To scale, a developer updates the RDS DB instance type in the pre-production CloudFormation stack. After deploying the update, the stack enters an UPDATE_ROLLBACK_FAILED state. What is the most likely cause?

An UPDATEROLLBACKFAILED state often indicates that CloudFormation encountered an issue when attempting to revert changes, leaving the stack in an inconsistent state. If the database was deleted or modified manually outside of CloudFormation, CloudFormation would be unable to find the resource it expects to roll back to, leading to this failure. An invalid instance type value would typically cause an UPDATEFAILED state during the initial update attempt, not UPDATEROLLBACKFAILED. A syntax error in the template would prevent the update from even starting or cause an initial UPDATEFAILED. Insufficient IAM permissions would also result in an UPDATEFAILED state during the update process itself, as CloudFormation wouldn't be authorized to make the change.