AWS Certified Solutions Architect – Associate (SAA-C03) — Question 492

A company has an application that processes customer orders. The company hosts the application on an Amazon EC2 instance that saves the orders to an Amazon Aurora database. Occasionally when traffic is high the workload does not process orders fast enough.

What should a solutions architect do to write the orders reliably to the database as quickly as possible?

Answer options

• A. Increase the instance size of the EC2 instance when traffic is high. Write orders to Amazon Simple Notification Service (Amazon SNS). Subscribe the database endpoint to the SNS topic.
• B. Write orders to an Amazon Simple Queue Service (Amazon SQS) queue. Use EC2 instances in an Auto Scaling group behind an Application Load Balancer to read from the SQS queue and process orders into the database.
• C. Write orders to Amazon Simple Notification Service (Amazon SNS). Subscribe the database endpoint to the SNS topic. Use EC2 instances in an Auto Scaling group behind an Application Load Balancer to read from the SNS topic.
• D. Write orders to an Amazon Simple Queue Service (Amazon SQS) queue when the EC2 instance reaches CPU threshold limits. Use scheduled scaling of EC2 instances in an Auto Scaling group behind an Application Load Balancer to read from the SQS queue and process orders into the database.

Correct answer: B

Explanation

Using Amazon SQS decouples the order ingestion from the database write process, ensuring that peak traffic is safely buffered and no orders are lost. An Auto Scaling group of EC2 instances can then scale dynamically to process messages from the queue as quickly as possible. Options involving Amazon SNS are incorrect because SNS cannot directly write to or integrate as a subscriber with an Amazon Aurora database endpoint.