Which solution will provide this connectivity in the MOST secure way?
Configure the Lambda function to use Amazon RDS Proxy outside the VPC.
Associate a security group with the Lambda function. Authorize this security group in the database’s security group.
Authorize the compute subnet’s CIDR ranges in the database’s security group.
During the initialization phase, authorize all IP addresses in the database’s security group temporarily. Remove the rule after the initialization is complete.
Explanations:
Configuring the Lambda function to use Amazon RDS Proxy outside the VPC does not provide direct connectivity to the database in the private subnet and may expose database traffic to the public internet, which is not secure.
Associating a security group with the Lambda function and authorizing this security group in the database’s security group allows for controlled access, ensuring that only the Lambda function can connect to the database while maintaining security through VPC security group rules.
Authorizing the compute subnet’s CIDR ranges in the database’s security group would expose the database to all resources in that subnet, potentially allowing unauthorized access from other services or instances, which is not a secure practice.
Authorizing all IP addresses temporarily during initialization increases the risk of unauthorized access. It creates a vulnerability that could be exploited while the rule is active, making this approach insecure.
I arrange that the answer is:
Associate a security group with the Lambda function. Authorize this security group in the database’s security group.