AWS Certified Solutions Architect – Associate (SAA-C03) — Question 689

A package delivery company has an application that uses Amazon EC2 instances and an Amazon Aurora MySQL DB cluster. As the application becomes more popular, EC2 instance usage increases only slightly. DB cluster usage increases at a much faster rate.

The company adds a read replica, which reduces the DB cluster usage for a short period of time. However, the load continues to increase. The operations that cause the increase in DB cluster usage are all repeated read statements that are related to delivery details. The company needs to alleviate the effect of repeated reads on the DB cluster.

Which solution will meet these requirements MOST cost-effectively?

Answer options

• A. Implement an Amazon ElastiCache for Redis cluster between the application and the DB cluster.
• B. Add an additional read replica to the DB cluster.
• C. Configure Aurora Auto Scaling for the Aurora read replicas.
• D. Modify the DB cluster to have multiple writer instances.

Correct answer: A

Explanation

Implementing an Amazon ElastiCache for Redis cluster is the most cost-effective solution because caching repeated read queries offloads the traffic from the database entirely, preventing unnecessary database scaling costs. Adding more read replicas or configuring Aurora Auto Scaling would increase costs continuously as database load grows, without addressing the root cause of redundant read queries. Modifying the cluster to have multiple writer instances is designed for write-heavy workloads and does not efficiently resolve a read-heavy bottleneck.