AWS Certified Solutions Architect – Professional (SAP-C02) — Question 302

A company runs its application on Amazon EC2 instances and AWS Lambda functions. The EC2 instances experience a continuous and stable load. The Lambda functions experience a varied and unpredictable load. The application includes a caching layer that uses an Amazon MemoryDB for Redis cluster.

A solutions architect must recommend a solution to minimize the company's overall monthly costs.

Which solution will meet these requirements?

Answer options

• A. Purchase an EC2 instance Savings Plan to cover the EC2 instances. Purchase a Compute Savings Plan for Lambda to cover the minimum expected consumption of the Lambda functions. Purchase reserved nodes to cover the MemoryDB cache nodes.
• B. Purchase a Compute Savings Plan to cover the EC2 instances. Purchase Lambda reserved concurrency to cover the expected Lambda usage. Purchase reserved nodes to cover the MemoryDB cache nodes.
• C. Purchase a Compute Savings Plan to cover the entire expected cost of the EC2 instances, Lambda functions, and MemoryDB cache nodes.
• D. Purchase a Compute Savings Plan to cover the EC2 instances and the MemoryDB cache nodes. Purchase Lambda reserved concurrency to cover the expected Lambda usage.

Correct answer: A

Explanation

EC2 Instance Savings Plans offer the deepest discounts (up to 72%) for stable, predictable EC2 workloads when compared to Compute Savings Plans. Compute Savings Plans are highly flexible and apply to AWS Lambda, making them ideal for covering the baseline of fluctuating Lambda workloads, while MemoryDB reserved nodes provide discounted rates for the caching layer. Reserved concurrency is a scaling and throttling mechanism rather than a cost-saving purchasing option, and Compute Savings Plans do not cover MemoryDB nodes.