AWS Certified Solutions Architect – Associate (SAA-C03) — Question 415

A company moved its on-premises PostgreSQL database to an Amazon RDS for PostgreSQL DB instance. The company successfully launched a new product. The workload on the database has increased. The company wants to accommodate the larger workload without adding infrastructure.

Which solution will meet these requirements MOST cost-effectively?

Answer options

• A. Buy reserved DB instances for the total workload. Make the Amazon RDS for PostgreSQL DB instance larger.
• B. Make the Amazon RDS for PostgreSQL DB instance a Multi-AZ DB instance.
• C. Buy reserved DB instances for the total workload. Add another Amazon RDS for PostgreSQL DB instance.
• D. Make the Amazon RDS for PostgreSQL DB instance an on-demand DB instance.

Correct answer: A

Explanation

Scaling up the instance size (vertical scaling) directly accommodates the larger workload without adding new infrastructure, and purchasing Reserved Instances provides the most cost-effective pricing for this steady-state workload. Adding another instance violates the requirement to not add infrastructure, while Multi-AZ is designed for high availability rather than performance scaling. On-Demand instances are significantly more expensive than Reserved Instances for a continuous, predictable workload.