What do resource-based policies allow in AWS?

Resource-based policies in AWS are a type of policy that you attach directly to resources like Amazon S3 buckets, AWS Lambda functions, Amazon SNS topics, and others to manage access to those specific resources. These policies allow you to define who can access the resource and what actions they can perform on it. This enables fine-grained control over resource security by specifying which AWS accounts, services, or users are granted permission to use those resources, thus allowing access management at the resource level rather than user or role level.

The ability to grant access is crucial, especially in multi-account architectures or when services need to interact securely. Through resource-based policies, you can set permissions that specify conditions under which actions can be taken on a resource, facilitating better security and management.

While managing IAM user roles, creating custom metrics for CloudWatch, and handling event notifications across services are important aspects of AWS management, they do not directly pertain to the functionality provided by resource-based policies. Resource-based policies are specifically focused on controlling access and permissions around AWS resources, making the option related to granting access to AWS resources the most accurate.