Which issues could be causing this problem?
(Choose two.)
The application instance’s security group is not allowing outbound traffic.
The network ACL of the application instance’s subnet is not allowing traffic between the application and the DB instance.
The VPC’s route table is not configured correctly.
There is no peering connection between the application and the database.
The DB instance’s security group is not allowing outbound traffic.
Explanations:
If the application instance’s security group does not allow outbound traffic, it will not be able to reach the DB.
Network ACLs control traffic at the subnet level, so if they block traffic between the subnets, communication will fail.
The route table is likely configured correctly if both instances are within the same VPC, as they use implicit routing.
A peering connection is unnecessary because both resources are in the same VPC.
Outbound rules on the DB instance’s security group do not affect incoming traffic to the DB instance.
From what I’ve heard, the answer is:
The application instance’s security group is not allowing outbound traffic.