An enterprise manages an AWS Organization with consolidated billing. The environment consi… — AWS Certified Solutions Architect - Professional

An enterprise manages an AWS Organization with consolidated billing. The environment consists of three member accounts with the following workloads:

* Account A (Web Application): A production web application running on Amazon EC2 instances in an Auto Scaling Group across $3$ Availability Zones. The instances are currently $c6i.xlarge$ ( $4$ vCPUs, $8$ GiB RAM). Metrics indicate average CPU utilization is $12\%$ and peak memory utilization is $3.5$ GiB.
* Account B (APIs): A containerized payment API workload running on AWS Fargate.
* Account C (Data Processing): An event-driven data pipeline using AWS Lambda.

To optimize outgoing internet traffic costs, the company wants to consolidate their NAT Gateway configuration, as each account currently has its own NAT Gateways deployed across $3$ Availability Zones. The solution must maintain high availability, maximize discount coverage for all compute workloads, and minimize administrative effort.

Which strategy should the Solutions Architect recommend to optimize resource costs and sizing while meeting these requirements?

In Account A, update the Auto Scaling Group launch template to use $c6i.large$ instances. In the AWS Organizations management account, purchase a Compute Savings Plan to cover compute costs across all accounts. Deploy redundant NAT Gateways across $3$ Availability Zones in a centralized VPC, share the private subnets with the member accounts using AWS Resource Access Manager (RAM), and configure the member account route tables to direct outbound internet traffic through the shared subnets.Answer
B
In Account A, update the Auto Scaling Group launch template to use $c6i.large$ instances. In the AWS Organizations management account, purchase a Compute Savings Plan to cover compute costs across all accounts. In Account A, use AWS Resource Access Manager (RAM) to share the NAT Gateways directly with the VPCs in Account B and Account C, and configure their route tables to direct outbound traffic through the shared NAT Gateways.
C
In Account A, update the Auto Scaling Group launch template to use $c6i.large$ instances. In the AWS Organizations management account, purchase a Compute Savings Plan to cover compute costs across all accounts. Deploy a single NAT Gateway in a centralized VPC, share the private subnets with the member accounts using AWS Resource Access Manager (RAM), and configure the member account route tables to direct all outbound traffic through the single NAT Gateway.
D
In Account A, update the Auto Scaling Group launch template to use $c6i.large$ instances. In the AWS Organizations management account, purchase an EC2 Instance Savings Plan for the $c6i$ family. Deploy redundant NAT Gateways across $3$ Availability Zones in a centralized VPC, share the private subnets with the member accounts using AWS Resource Access Manager (RAM), and configure the member account route tables to direct outbound internet traffic through the shared subnets.

Answer

The correct strategy is to resize the EC2 instances to

c6i.large

, purchase a Compute Savings Plan in the management account to cover the EC2, Fargate, and Lambda workloads, and consolidate outbound traffic by deploying redundant NAT Gateways in a centralized VPC and sharing those subnets via AWS Resource Access Manager (RAM).

The correct option correctly addresses all constraints. Sizing down the EC2 instances to

c6i.large

aligns resource capacity with actual utilization (since peak memory is

3.5

GiB and average CPU is very low). A Compute Savings Plan is the only Savings Plan type that covers EC2, Fargate, and Lambda across all member accounts under consolidated billing. Finally, sharing subnets containing redundant NAT Gateways via AWS RAM is the supported method to consolidate NAT Gateway costs while maintaining high availability across multiple Availability Zones.

Step-by-Step Solution

Determine the right-sizing target for the EC2 instances in Account A.

The current instances are

c6i.xlarge

(

4

vCPUs,

8

GiB RAM) with average CPU utilization of

12\%

(requiring less than

0.5

vCPUs on average) and a peak memory of

3.5

GiB. Sizing down to

c6i.large

(

2

vCPUs,

4

GiB RAM) meets both requirements safely while reducing resource waste.

Right-sizing should always precede purchasing Savings Plans to avoid over-committing to unnecessary capacity.

Evaluate the compute types across the multi-account organization to determine the most cost-effective Savings Plan type.

The workloads span EC2 instances (Account A), AWS Fargate tasks (Account B), and AWS Lambda functions (Account C). Only a Compute Savings Plan applies discount coverage to all three compute types across the organization's consolidated billing.

EC2 Instance Savings Plans do not apply to serverless workloads (Fargate and Lambda) and would leave Accounts B and C without coverage.

Select a highly available and cost-optimized outbound routing strategy for the member accounts.

Deploy redundant NAT Gateways across

3

Availability Zones in a centralized VPC, share the subnets via AWS Resource Access Manager (RAM), and route outbound traffic from the member VPCs through these subnets.

This consolidates NAT Gateway costs while maintaining high availability across Availability Zones without attempting unsupported direct sharing of NAT Gateway resources via RAM.

Key Concept

Compute cost optimization requires a combination of instance right-sizing and choosing the correct Savings Plan type based on workload variety, while network cost optimization must preserve high availability.

Alternative Method

Use AWS Compute Optimizer to automatically analyze historical utilization metrics and recommend the optimal instance types for the Auto Scaling Group, ensuring that CPU and memory headroom are preserved while minimizing costs.

Estimated Time:2m 0s

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