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Question

Difficulty: MediumManaging Storage and Data Transfer Costs

An enterprise operates a high-throughput application on Amazon EC2 instances in private subnets across 33 Availability Zones in the `us-east-1` Region. The application regularly pulls raw data sets from an Amazon S3 bucket, processes them, and writes the results to another S3 bucket in the same Region. Currently, outbound traffic to S3 is routed through a single NAT Gateway located in one of the public subnets. This setup processes approximately 80 TB80\text{ TB} of data monthly, leading to significant NAT Gateway data processing charges. Which of the following solutions is the most cost-effective and architecturally sound method to minimize these data transfer costs?

  1. A
    Replace the existing NAT Gateway with an Amazon S3 Interface VPC Endpoint in each of the 33 Availability Zones, and update the private route tables to target the interface endpoints.
  2. Create an Amazon S3 Gateway VPC Endpoint in the VPC, and associate it with the route tables of the private subnets to route S3 traffic directly.Answer
  3. C
    Deploy an AWS Transit Gateway, connect it to the VPC, and route all S3-bound traffic through a central egress VPC that hosts S3 Interface Endpoints.
  4. D
    Purchase a Compute Savings Plan to cover the S3 data transfer and processing costs from the NAT Gateway, while retaining the current routing architecture.

Answer

Create an Amazon S3 Gateway VPC Endpoint in the VPC, and associate it with the route tables of the private subnets to route S3 traffic directly.
Creating a Gateway VPC Endpoint for S3 is the most cost-effective solution because S3 Gateway Endpoints do not incur any hourly or data processing charges. By associating the endpoint with the private subnet route tables, S3-bound traffic is routed directly to the regional S3 service over the AWS network, bypassing the NAT Gateway and eliminating the associated processing charges.

Step-by-Step Solution

1
Analyze the current data path and cost drivers.
The application transfers 80 TB80\text{ TB} of data to and from S3 through a NAT Gateway, which incurs a processing fee of $0.045 per GB\$0.045\text{ per GB} in the `us-east-1` Region.
Identifying the primary source of the cost is necessary to determine the appropriate optimization target.
2
Evaluate AWS VPC endpoints for S3 traffic.
Gateway VPC Endpoints for S3 are free and route traffic privately without traversing a NAT Gateway, whereas Interface VPC Endpoints incur hourly and processing fees ($0.01 per GB\$0.01\text{ per GB}).
Choosing the endpoint type with the lowest cost model is essential for achieving optimal savings.
3
Configure routing to bypass the NAT Gateway for S3.
Create a Gateway VPC Endpoint for S3 and associate it with the private subnet route tables. This automatically adds a route pointing to S3 via the prefix list.
Updating route tables ensures that only S3-destined traffic bypasses the NAT Gateway, maintaining external internet access for other traffic.

Key Concept

VPC Gateway Endpoints provide a secure, cost-free mechanism to access Amazon S3 and DynamoDB without routing traffic through a NAT Gateway, NAT instance, or virtual private gateway.
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Topics

Managing Storage and Data Transfer Costs