You have deployed a new Lambda Function and an RDS MySQL database. The Lambda is not configured in any VPC and has internet access. As the Lambda Function needs to communicate with the RDS database to fetch data, you configure the Lambda Function in the private subnet where the database resides. However, after that, the Lambda Function has lost the internet connection. How would you resolve this problem?

Answer options:

A.In the VPC private subnet, route the outbound traffic to a NAT gateway in a public subnet.
B.Create VPC endpoints for all the services that the Lambda Function needs to access.
C.Do not attach the VPC access to the Lambda Function as, by default, the Lambda Function has the internet access.
D.Attach an Internet gateway to the public subnet of the VPC. Modify the route table to use the internet gateway for all inbound and outbound traffic.
 

Correct Answer – A
Refer to https://docs.aws.amazon.com/lambda/latest/dg/configuration-vpc.html for how to configure a Lambda Function to access resources in a VPC. You can configure the Lambda Function to access to a VPC as below:
Option A is CORRECT: Because when a function is attached in the private subnet, it does not have access to the internet unless the VPC provides access. The NAT Gateway can provide the internet access for the resources in the private gateway.
Option B is incorrect: In this question, the Lambda function needs the internet access. It does not mention that it needs to access other AWS services. VPC endpoints cannot fulfill the requirements.
Option C is incorrect: Because if the Lambda function is not attached to the VPC, it cannot communicate with the RDS instance. However, the Lambda function needs to fetch data from the RDS database.
Option D is incorrect: Because the NAT gateway should be used for the resources in the private subnet to connect to the internet. Attaching an internet gateway in the public subnet does not help.