Which service is primarily responsible for managing user access to AWS resources?

The service that is primarily responsible for managing user access to AWS resources is AWS Identity and Access Management (IAM). IAM allows you to create and manage AWS users and groups, and assign them the appropriate access permissions to various AWS resources. This means you can control who can access specific services and resources, and under what conditions, enhancing the security and management of your AWS environment.

By using IAM, organizations can implement the principle of least privilege, ensuring that users have only the permissions they need to perform their job functions. IAM also supports features such as multi-factor authentication (MFA) for enhanced security and identity federation, which allows users to access AWS resources using existing credentials from other identity providers.

The other services mentioned have different primary functions. AWS CloudFormation is used for deploying and managing infrastructure as code, AWS Systems Manager provides operational management capabilities for AWS resources, and AWS Config helps with resource inventory management and compliance auditing. These services do not specifically focus on user access management like IAM does.