In addition to automated backup, you can always initiate a manual snapshot of the DB instance at any time. The manual snapshot that you take does not get deleted when you delete the DB instance, and does not come under the AWS Managed Service umbrella. All automated snapshots are deleted when you delete the DB instance. You can retain the copy of a manual snapshot for as long as you want. Usually, you can always initiate the manual snapshot before making any changes to the DB instance. You can initiate the manual snapshot using the following command:
PS C:\> New-RDSDBSnapshot -DBSnapshotIdentifier "before-change-mywebappprd" -DBInstanceIdentifier "mywebappprd"
The DB instance is available during the manual snapshot process. In this case, backups will also be taken on the standby site if you have a Multi-AZ configuration...