AWS Certified Developer – Associate — Question 291

A company has a three-tier application that is deployed in Amazon Elastic Container Service (Amazon ECS). The application is using an Amazon RDS for MySQL DB instance. The application performs more database reads than writes.

During times of peak usage, the application’s performance degrades. When this performance degradation occurs, the DB instance’s ReadLatency metric in Amazon CloudWatch increases suddenly.

How should a developer modify the application to improve performance?

Answer options

• A. Use Amazon ElastiCache to cache query results.
• B. Scale the ECS cluster to contain more ECS instances.
• C. Add read capacity units (RCUs) to the DB instance.
• D. Modify the ECS task definition to increase the task memory.

Correct answer: A

Explanation

Implementing Amazon ElastiCache allows the application to cache frequently accessed query results, significantly reducing the read load and high ReadLatency on the Amazon RDS for MySQL DB instance. Scaling ECS instances or task memory would not resolve the database-tier bottleneck. Additionally, Read Capacity Units (RCUs) are a feature of Amazon DynamoDB and do not apply to Amazon RDS.