You’ve set up an RDS Instance. An application is being hosted on an EC2 Instance that connects to the AWS RDS Instance. From the application, the following error is being encountered.
“Error connecting to database”
You’ve verified that you can connect to the database from a bastion host in a public subnet via the AWS Console. Which of the following could be possible issues? Choose 2 answers from the options given below

Answer options:

A.The application is using the wrong port number in the connection string.
B.The database server has the wrong ingress Security group rule for the web server.
C.The database server has the wrong egress Security group rule for the web server.
D.The database is stopped.

Correct Answers: A and B
The AWS Documentation mentions the following.
When you cannot connect to a DB instance, the following are common causes.
· The access rules enforced by your local firewall and the ingress IP addresses you authorized to access your DB instance in the instance`s security group are not in sync. The problem is most likely the ingress rules in your security group. By default, DB instances do not allow access; access is granted through a security group. To grant access, you must create your own security group with specific ingress and egress rules for your situation.
· The port you specified when you created the DB instance cannot be used to send or receive communications due to your local firewall restrictions. In this case, check with your network administrator to determine if your network allows the specified port to be used for inbound and outbound communication.
· Your DB instance is still being created and is not yet available. Depending on the size of your DB instance, it can take up to 20 minutes before an instance is available.
Option C is incorrect because the connection comes from the application to the database. As the Security group is stateful, only the ingress rule needs to allow the connection.
Option D is incorrect because if the database is stopped, you cannot connect to the bastion host`s database.
For more information on troubleshooting connecting to AWS RDS, please refer to the below URL-
https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/CHAP_Troubleshooting.html#CHAP_Troubleshooting.Connecting