AWS Certified Solutions Architect – Associate (SAA-C02) — Question 549

A solutions architect is designing a shared storage solution for a web application that is deployed across multiple Availability Zones. The web application runs on
Amazon EC2 instances that are in an Auto Scaling group. The company plans to make frequent changes to the content. The solution must have strong consistency in returning the new content as soon as the changes occur.
Which solutions meet these requirements? (Choose two.)

Answer options

• A. Use AWS Storage Gateway Volume Gateway Internet Small Computer Systems Interface (iSCSI) block storage that is mounted to the individual EC2 instances.
• B. Create an Amazon Elastic File System (Amazon EFS) file system. Mount the EFS file system on the individual EC2 instances.
• C. Create a shared Amazon Elastic Block Store (Amazon EBS) volume. Mount the EBS volume on the individual EC2 instances.
• D. Use AWS DataSync to perform continuous synchronization of data between EC2 hosts in the Auto Scaling group.
• E. Create an Amazon S3 bucket to store the web content. Set the metadata for the Cache-Control header to no-cache. Use Amazon CloudFront to deliver the content.

Correct answer: B, E

Explanation

Amazon EFS provides a shared file system that can be concurrently mounted on multiple EC2 instances across multiple Availability Zones with strong consistency. Amazon S3 also offers strong read-after-write consistency, and by setting the Cache-Control header to 'no-cache', CloudFront is forced to revalidate the content with the S3 origin for every request, ensuring immediate delivery of updates. Standard EBS volumes cannot be shared across multiple AZs, Storage Gateway is not suitable for this multi-instance architecture, and AWS DataSync is an offline/scheduled transfer tool rather than a real-time synchronous storage solution.