You must create a REST API using AWS API Gateway with Lambda as backend system and Oracle RDS instance as database. You have created API methods, Lambda function code and spun up Oracle RDS instance in a private VPC with no Internet Gateway. When you are trying to connect to the RDS instance from your Lambda, the connection getting failed. What could be the reason? (choose 2 options)

Answer options:

A.Lambda execution role does not have policy to access RDS instance.
B.Lambda function is running in “no VPC” network mode.
C.RDS instance security group is not allowing connections from Lambda subnet range.
D.RDS instance is not configured as destination in Lambda setup.

Answer: B, C
Option A is not correct. A policy on the role can only define access to which API actions can be made on RDS instance such as rds:CreateDBInstance, rds:CreateDBSecurityGroup, rds:CreateDBSnapshot etc. The policy will not define whether a resource can connect to an RDS instance or not.
Option B is correct. When the Lambda function runs in “no VPC” network mode, it will not have access to resources running in a private VPC.
https://docs.aws.amazon.com/lambda/latest/dg/vpc.html
Option C is correct. Security groups act as a firewall for any resources (such as RDS instance and Lambda in this case) they are connected with. If there is no inbound rule defined to allow connections from the Lambda subnet IP range or the Lambda security group, connections will fail.
https://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/VPC_SecurityGroups.html
Option D is not correct. There is no such configuration for the destination in the Lambda setup.