How can the developer solve this problem?
Modify the RDS security group. Add a rule to allow traffic from all the ports from the VPC CIDR block.
Redeploy the Lambda function in the same subnet as the RDS instance. Ensure that the RDS security group allows traffic from the Lambda function.
Create a security group for the Lambda function. Add a new rule in the RDS security group to allow traffic from the new Lambda security group.
Create an IAM role. Attach a policy that allows access to the RDS database. Attach the role to the Lambda function.
Explanations:
Modifying the RDS security group to allow traffic from all ports of the VPC CIDR block does not solve the issue because the Lambda function is in a different VPC (default VPC), which would not route traffic to the RDS instance in VPC-A. Security group rules cannot bridge VPCs.
Redeploying the Lambda function in the same VPC (VPC-A) as the RDS instance ensures that the function can access the RDS database directly. Additionally, the RDS security group must allow traffic from the Lambda function’s security group to establish a connection.
Creating a security group for the Lambda function and allowing traffic from it to the RDS security group would not resolve the issue unless the Lambda function is also moved to the same VPC as the RDS instance. Without being in the same VPC, the traffic will not reach the RDS instance.
While creating an IAM role with the necessary permissions for the Lambda function to access the RDS database is important for authorization, it does not address the connectivity issue. The Lambda function must be in the same VPC as the RDS instance for the connection to succeed.
I guess:
Redeploy the Lambda function in the same subnet as the RDS instance. Ensure that the RDS security group allows traffic from the Lambda function.