It is a web service running in the cloud and provides relational database for use in Alfresco Content Services. Amazon RDS supports and gives you online access to the capabilities of a MySQL, Oracle, Microsoft SQL Server, PostgreSQL, or Amazon Aurora relational database management system.
As a good practice, when using Amazon EC2 environment you may want to use S3 bucket for content store. For more information, see Alfresco Content Connector for AWS S3.
For configuring different databases for Amazon RDS, see the topics below.