Each RDS instance has a unique identifier. This unique identifier is the RDS instance's ID.
If you created your RDS instance using the AWS Management Console, the RDS instance ID is the name of your RDS instance that you supplied in the "DB Instance Identifier" field:
If you created your RDS instance using tools such as CloudFormation, your RDS instance ID may have been automatically generated.
When viewing the list of RDS instances in the AWS Management Console, the RDS instance ID for your instances is located in the "DB Instance" column.
You will also see your RDS instance ID at the end of the RDS instance ARN after