AWS Certified Solutions Architect – Associate (SAA-C02) — Question 722

A company is hosting a web application on AWS using a single Amazon EC2 instance that stores user-uploaded documents in an Amazon Elastic Block Store
(Amazon EBS) volume. For better scalability and availability, the company duplicated the architecture and created a second EC2 instance and EBS volume in another Availability Zone, placing both behind an Application Load Balancer. After completing this change, users reported that each time they refreshed the website, they could see one subset of their documents or the other, but never all of the documents at the same time.
What should a solutions architect propose to ensure users see all of their documents at once?

Answer options

• A. Copy the data so both EBS volumes contain all the documents.
• B. Configure the Application Load Balancer to direct a user to the server with the documents.
• C. Copy the data from both EBS volumes to Amazon Elastic File System (Amazon EFS). Modify the application to save new documents to Amazon Elastic File System (Amazon EFS).
• D. Configure the Application Load Balancer to send the request to both servers. Return each document from the correct server.

Correct answer: C

Explanation

Amazon EBS volumes are block-level storage devices that can only be attached to a single EC2 instance at a time within a single Availability Zone, making them unsuitable for sharing files across multiple instances. Amazon Elastic File System (Amazon EFS) provides a shared, concurrent-access file system that can be mounted by multiple EC2 instances across different Availability Zones. Migrating the files to EFS and updating the application ensures that both web servers have access to a single, consistent repository of all user-uploaded documents.