AWS Certified CloudOps Engineer Associate SOA-C03 Practice Question

An online game backend uses a db.t3.medium Amazon RDS for MySQL 8.0 instance. CloudWatch shows frequent burst‐credit exhaustion and high ReadIOPS, while Performance Insights reports a buffer cache hit ratio below 80 percent. Developers cannot change application code and want the least expensive change to improve query latency during peak hours. Which action meets these requirements?

Upgrade the instance to db.m6g.large to add more vCPU and memory capacity.
Increase the value of innodb_buffer_pool_size in a custom DB parameter group and reboot the instance during the maintenance window.
Turn on 7-day retention for Performance Insights to analyze historical wait events.
Enable CloudWatch detailed monitoring at 1-minute granularity to get finer performance metrics.

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Answer Description

The low buffer cache hit ratio indicates that most reads are going to disk. On MySQL, the InnoDB buffer pool keeps indexes and data pages in memory; enlarging it sharply reduces physical I/O, lowering CPU and storage throughput usage. Creating a custom DB parameter group with a larger innodb_buffer_pool_size and applying it to the instance adds no recurring cost (other than the small downtime for the scheduled reboot) and directly addresses the root cause. The other options either only provide additional monitoring data, incur higher instance or storage charges, or do not target the excessive disk reads.

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