AWS Certified Solutions Architect – Associate (SAA-C03) — Question 377

A solutions architect is creating a new VPC design. There are two public subnets for the load balancer, two private subnets for web servers, and two private subnets for MySQL. The web servers use only HTTPS. The solutions architect has already created a security group for the load balancer allowing port 443 from 0.0.0.0/0. Company policy requires that each resource has the least access required to still be able to perform its tasks.

Which additional configuration strategy should the solutions architect use to meet these requirements?

Answer options

• A. Create a security group for the web servers and allow port 443 from 0.0.0.0/0. Create a security group for the MySQL servers and allow port 3306 from the web servers security group.
• B. Create a network ACL for the web servers and allow port 443 from 0.0.0.0/0. Create a network ACL for the MySQL servers and allow port 3306 from the web servers security group.
• C. Create a security group for the web servers and allow port 443 from the load balancer. Create a security group for the MySQL servers and allow port 3306 from the web servers security group.
• D. Create a network ACL for the web servers and allow port 443 from the load balancer. Create a network ACL for the MySQL servers and allow port 3306 from the web servers security group.

Correct answer: C

Explanation

To enforce the principle of least privilege, the web servers should only receive traffic from the load balancer rather than the entire internet, and the database should only receive traffic from the web servers. Security groups are stateful and support referencing other security groups as traffic sources, making Option C the correct and most secure choice. Network ACLs are stateless and cannot reference security groups as sources, which rules out Options B and D.