Which service is used for configuring and managing shared resources across AWS accounts and organizational units?

The service used for configuring and managing shared resources across AWS accounts and organizational units is AWS Resource Access Manager (AWS RAM). AWS RAM is specifically designed to enable the sharing of resources such as VPC subnets, transit gateways, and more, seamlessly across different AWS accounts. This makes it an ideal tool for organizations that operate multiple accounts within AWS Organizations.

AWS RAM allows users to create resource shares and manage permissions, ensuring that shared resources are utilized efficiently and securely. By using AWS RAM, organizations can achieve better resource management and optimize costs by leveraging shared resources across various accounts rather than duplicating them.

Other services mentioned, such as AWS Directory Service, focus on directory management and integration with Active Directory, AWS Identity and Access Management (IAM) deals with access control and permissions within a single account, and AWS Firewall Manager is for centralized management of firewall rules across accounts. While these services have their own distinct purposes, none are specifically designed for the cross-account resource sharing capabilities that AWS RAM provides.