SAA-C03 Design Cost-Optimized Architectures Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✓

  Create a Gateway VPC Endpoint for Amazon S3.

  Why this is correct

  Gateway Endpoints for S3 are provided at no additional cost and do not incur data processing charges. By routing S3 traffic through the endpoint instead of the NAT Gateway, the company eliminates the per-GB processing fee for all data transfers to and from S3, leading to massive cost savings.

• ✗

  Replace the NAT Gateway with a NAT Instance.

  Why it's wrong here

  While a NAT Instance might be cheaper in terms of hourly instance costs compared to a NAT Gateway, it does not solve the fundamental cost issue of high-volume data transfer. NAT Instances also require manual management, scaling, and high-availability configuration, which increases operational overhead without providing the zero-cost benefit of a Gateway Endpoint.

• ✓

  Update the route table to direct S3 traffic through the Gateway Endpoint.

  Why this is correct

  Creating a Gateway Endpoint is only the first step; you must also update the route tables of the private subnets to point S3-bound traffic (using a prefix list) to the endpoint. This ensures that the instances automatically use the more cost-effective path instead of defaulting to the NAT Gateway.

• ✗

  Move the EC2 instances to public subnets.

  Why it's wrong here

  Moving instances to public subnets and using an Internet Gateway would eliminate NAT Gateway costs, but it severely compromises security. Public subnets expose instances to the internet, increasing the attack surface. Cost optimization must be balanced with security requirements, and VPC Endpoints are the architecturally sound solution here.

• ✗

  Increase the number of NAT Gateways across all Availability Zones.

  Why it's wrong here

  Increasing the number of NAT Gateways would improve availability and potentially bandwidth, but it would actually increase costs. Each NAT Gateway has an hourly charge. To reduce costs, the goal is to decrease the amount of data flowing through the NAT service, not to provision more of it.