Which solution is MOST secure?
Create an Amazon Cognito user pool for the mobile app users. Attach an IAM policy that has the required DynamoDB permissions to the user pool.
Create an AWS Lambda authorizer with the required DynamoDB permissions. Attach the Lambda authorizer to the Application Load Balancer.
Create an IAM user for each mobile user. Attach an IAM policy that provides the required DynamoDB permissions to each IAM user.
Create an IAM role. Attach a policy with the required DynamoDB permissions to the role. Configure the EC2 Auto Scaling launch template to attach the role to all EC2 instances.
Explanations:
Amazon Cognito user pools are used for user authentication and management, but they do not directly provide permissions to access AWS resources like DynamoDB. You would need to integrate Cognito with AWS IAM roles to allow access to DynamoDB.
AWS Lambda authorizers are used for API Gateway or other authentication needs, not for directly managing access to DynamoDB. Additionally, the Application Load Balancer is not the appropriate place to configure permissions for DynamoDB access.
Creating an IAM user for each mobile app user would be impractical and inefficient. IAM users are typically used for AWS services or human access, not for mobile apps. This approach does not scale well and would require managing many individual IAM users.
The most secure and efficient solution is to create an IAM role with the necessary DynamoDB permissions and assign this role to the EC2 instances through the Auto Scaling launch template. This ensures that only the EC2 instances, not individual users or the load balancer, have the appropriate permissions to access DynamoDB.
I systematize that the answer is:
Create an IAM role. Attach a policy with the required DynamoDB permissions to the role. Configure the EC2 Auto Scaling launch template to attach the role to all EC2 instances.