AWS Certified Solutions Architect – Professional — Question 334

A company is planning a large event where a promotional offer will be introduced. The company's website is hosted on AWS and backed by an Amazon RDS for
PostgreSQL DB instance. The website explains the promotion and includes a sign-up page that collects user information and preferences. Management expects large and unpredictable volumes of traffic periodically, which will create many database writes. A solutions architect needs to build a solution that does not change the underlying data model and ensures that submissions are not dropped before they are committed to the database.
Which solution meets these requirements?

Answer options

• A. Immediately before the event, scale up the existing DB instance to meet the anticipated demand. Then scale down after the event.
• B. Use Amazon SQS to decouple the application and database layers. Configure an AWS Lambda function to write items from the queue into the database.
• C. Migrate to Amazon DynamoDB and manage throughput capacity with automatic scaling.
• D. Use Amazon ElastiCache for Memcached to increase write capacity to the DB instance.

Correct answer: B

Explanation

Using Amazon SQS decouples the application from the database by acting as a buffer, ensuring that sudden spikes in write requests are queued safely without being dropped. AWS Lambda can then pull items from the queue and write them to the Amazon RDS PostgreSQL database at a controlled rate. Option A does not handle unpredictable spikes reliably, Option C violates the requirement to keep the underlying data model unchanged, and Option D is incorrect because Memcached is a read cache and cannot protect writes from being dropped.