You are hired as an AWS engineer. Your major responsibility is to migrate existing services to the AWS platform. The company’s on-premises main page is made of Node.js and PostgreSQL database. You just migrated the frontend and backend to an EC2 instance. Also, you created a PostgreSQL instance in RDS.

Answer options:

A.Check that if the hostname is the DB instance endpoint and the port number is correct.
B.Check if the AWS SDK version is correct as there are issues for certain versions to communicate with RDS instances.
C.Check if the RDS instance has configured enough read and write capacity. If not, the “Connection timed out” issue may appear.
D.Check that the security group assigned to the DB instance has the necessary rules to allow access through the EC2 instance.

Correct Answer A, D
https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/CHAP_Troubleshooting.html#CHAP_Troubleshooting.SQLServer.Connect is a user guide on how to troubleshoot the RDS issues.
Option A is CORRECT: Because if the used endpoint or port is incorrect, the error would be “Connection timed out”.
Option B is incorrect: Because the AWS SDK version does not cause the issue to communicate with the RDS instance.
Option C is incorrect: Because the low configured capacity does not lead to a “Connection timed out” issue.
Option D is CORRECT: Because the most common problem when attempting to connect to a PostgreSQL DB instance is that the security group assigned to the DB instance has incorrect access rules.