Amazon RDS for SQL Server Now Supports Joining a Domain Across AWS Accounts and VPCs using Managed Microsoft AD
Starting today, Amazon RDS for SQL Server supports joining DB instances to an AWS Managed Microsoft AD directory residing in a different AWS account or VPC. This makes it easier and cost-effective for you to deploy your directory-aware database workloads by reducing the manual configuration to domain join your DB instances and, the need to deploy directories in each account and VPC. Amazon RDS for SQL Server DB instances can now seamlessly join to a directory from any AWS account and any Amazon VPC within an AWS Region.
Source:: Amazon AWS