Which set of actions should the database specialist take on the DB cluster to meet these requirements?

Explanations:

Disabling the automated backup feature by changing the retention period to 0 days would stop the automatic backups, which would lead to no backup storage being retained. This can cause the loss of valuable backup data and is not a good solution. Manual snapshots would require regular management, and the process would not automatically optimize costs.

Changing the backup retention period to 1 day will reduce the number of automated backups retained, thereby minimizing storage costs. The manual snapshots can be managed separately, and old snapshots can be deleted to optimize storage. This solution meets the requirements of cost optimization without causing downtime.

Keeping the backup retention period at 10 days does not reduce backup storage costs significantly, as it retains backups for a longer period. Deleting old manual snapshots would help, but the primary concern of reducing automated backup storage is not addressed effectively.

Disabling the automated backup feature by setting the retention period to 0 days will stop automated backups, which can lead to no backup being retained. Creating a backup plan in AWS Backup to perform daily backups would create a manual process that may be more complex and not as cost-effective as the automated method with a shorter retention period.