Which AWS service or feature should the company use to meet these authentication requirements?

Explanations:

Amazon API Gateway is primarily used to create and manage APIs for serverless applications and does not provide temporary credentials for authenticating to other AWS services. It can integrate with IAM for authentication but does not directly issue credentials.

IAM users are long-term credentials associated with a specific user or application. They do not provide temporary credentials and require careful management of access keys and permissions, which is not suitable for scenarios needing limited-privilege and temporary access.

AWS Security Token Service (AWS STS) provides temporary, limited-privilege credentials for AWS services. It allows the application to assume roles and obtain short-lived security credentials that can be used for authentication with AWS APIs, making it ideal for this requirement.

IAM instance profiles allow EC2 instances to assume a role and access AWS services, but they do not directly provide temporary credentials outside the context of the instance. They are more suitable for granting permissions to applications running on EC2 rather than for a general application needing temporary access to multiple AWS APIs.