Exam AWS Certified Solutions Architect - Associate SAA-C03 topic 1 question 417 discussion

Answer C is the best solution that meets the company’s requirements. By purchasing a Compute Savings Plan, the company can save on the costs of running both EC2 instances and Lambda functions. The Lambda functions can be connected to the private subnet that contains the EC2 instances through a VPC endpoint for AWS services or a VPC peering connection. This provides direct network access to the EC2 instances while keeping the traffic within the private network, which helps to minimize network latency. Optimizing the Lambda functions’ duration, memory usage, number of invocations, and amount of data transferred can help to further minimize costs and improve performance. Additionally, using a private subnet helps to ensure that the EC2 instances are not directly accessible from the public internet, which is a security best practice.

Implement Compute Savings Plan because it applies to Lambda usage as well, then connect the Lambda functions to the private subnet that contains the EC2 instances

"Savings Plans are a flexible pricing model that offer low prices on Amazon EC2, AWS Lambda, and AWS Fargate usage, in exchange for a commitment to a consistent amount of usage (measured in $/hour) for a 1 or 3 year term." - That already excludes A and B. The question requires to "keep network latency between the services low", which can be achieved by connecting the Lambda functions to the private subnet that contains the EC2 instances. C is the answer.

C https://aws.amazon.com/savingsplans/compute-pricing/

A Compute Savings Plan covers both EC2 and Lambda and allows maximizing savings on all resources. Optimizing Lambda configuration reduces costs. Connecting the Lambda functions to the private subnet with the EC2 instances provides direct network access between them, keeping latency low. The Lambda functions are isolated in the private subnet rather than public, improving security.

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Connect Lambda to Private Subnet contains EC2

Compute savings plan covers both EC2 & Lambda

C. I would go with C, because Compute savings plans cover Lambda as well.

A. I would go with A. Saving and low network latency are required. EC2 instance savings plans offer savings of up to 72% Compute savings plans offer savings of up to 66% Placing Lambda on the same private network with EC2 instances provides the lowest latency.