RDS Exam Tips

The main thing to remember for the exam is that if you're given an exam scenario where you've setup an RDS instance (e.g. MySQL) and have a PHP script on a separate EC2 instance in a different security group. When attempting to connect to the RDS instance from the php script, you get a connection error; why can't you connect. The answer is simply because these are two different security groups who can't talk to each other. To resolve the issue, you would modify the RDS instance's security group to allow incoming traffic on the MySQL port. You would restrict this security group rule to the security group that the EC2 instance is in, so that other sources can't access the DB.