How can a developer meet these requirements?

Explanations:

An Amazon Cognito identity pool provides temporary AWS credentials for unauthenticated users and authenticated users, but it is not specifically designed for managing user authentication and token expiration for REST APIs. It does not directly handle user sign-up and sign-in, which is typically managed by a user pool.

Maintaining a database record for each user with a corresponding token increases complexity and security risks. Using a Lambda authorizer is also less efficient and scalable compared to using a managed service like Amazon Cognito for user management and token validation.

An Amazon Cognito user pool provides user management features, including registration, authentication, and automatic token expiration and refresh. By configuring the Cognito Authorizer in API Gateway, the application can securely authorize registered users to access the API resources using the identity or access tokens generated by the user pool.

Creating IAM users for each API user is not scalable and goes against best practices for user authentication in applications. IAM is intended for managing AWS resources, not for managing application users, and using IAM roles would not facilitate automatic token expiration and refresh.