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SAA-C03 Practice Question 50: RDS Reserved Instances

AWS Certified Solutions Architect – Associate (SAA-C03) · Test 5 · question 10 of 10

Database Cost Optimizationeasy

A company runs two Amazon RDS for PostgreSQL instances that have been the same size for two years and run continuously. Finance has approved a one-year commitment in exchange for a lower rate. The databases cannot be paused, and the team does not expect the instance class to change.

What should the solutions architect recommend to reduce the cost of these databases?

Select one answer
Show answer and explanation

Answer:

  • A. Purchase Reserved DB Instances matching the instance class, Region and database engine

Reserved DB Instances are the commitment-based discount for Amazon RDS. A one-year reservation matched to the instance class, Region and engine that the workload already runs discounts the hourly rate substantially compared with On-Demand, and it suits a footprint that has been stable for two years and is expected to stay that way. Nothing about the running databases changes; the reservation is a billing construct applied to matching usage.

Option B is an architectural change aimed at variable or intermittent load. These instances run continuously at a steady size, so there is little idle capacity for serverless scaling to reclaim, and the migration carries risk the cost goal does not justify.

Option C names the wrong purchase model. Compute Savings Plans cover EC2, Fargate and Lambda; they do not apply to RDS instance hours.

Option D contradicts the stated constraint that the databases cannot be paused, and stopped RDS instances continue to incur storage charges.

Reference: Working with reserved DB instances

Practice Test 5 ›

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