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Difficulty: HardData Transfer Cost Optimization

A fleet of application servers resides in a private subnet within Spoke VPC A. The servers regularly write large analytics payloads to an Amazon DynamoDB table in the same AWS Region. The network topology utilizes a hub-and-spoke model where Spoke VPC A is connected to a central Hub VPC via an AWS Transit Gateway, and all internet-bound traffic is routed through a centralized NAT Gateway in the Hub VPC. The SysOps administrator identifies that this DynamoDB write traffic is incurring both Transit Gateway and NAT Gateway data processing charges, significantly inflating the monthly bill. Which configuration will eliminate the data processing charges for this traffic in the most cost-effective manner?

  1. Create a Gateway VPC endpoint for DynamoDB in Spoke VPC A, and select the private subnet's route table during creation to automatically add the route.Answer
  2. B
    Deploy an Interface VPC endpoint (AWS PrivateLink) for DynamoDB in Spoke VPC A, and update the private subnet's route table to route DynamoDB traffic to the endpoint network interface.
  3. C
    Create a Gateway VPC endpoint for DynamoDB in Spoke VPC A, but do not associate it with any route tables, and instead add a manual route pointing to the endpoint's Elastic Network Interface (ENI).
  4. D
    Deploy a local NAT Gateway in a public subnet within Spoke VPC A, and update the private subnet's route table to direct DynamoDB traffic through the local NAT Gateway.

Answer

Create a Gateway VPC endpoint for DynamoDB in Spoke VPC A, and select the private subnet's route table during creation to automatically add the route.
The correct option is to create a Gateway VPC endpoint and associate it with the private subnet's route table. Gateway endpoints are free and route DynamoDB traffic privately, avoiding the processing charges of both the Transit Gateway and the NAT Gateway.

Step-by-Step Solution

1
Analyze the current traffic path and identify charges.
DynamoDB traffic from Spoke VPC A routes through the Transit Gateway to the Hub VPC NAT Gateway. This incurs a Transit Gateway processing fee of 0.020.02 per GB and a NAT Gateway processing fee of 0.0450.045 per GB.
Understanding the baseline flow exposes the origin of the high costs.
2
Evaluate private routing options for DynamoDB.
DynamoDB supports Gateway VPC endpoints, which are free and do not incur data processing or hourly charges, unlike Interface VPC endpoints (PrivateLink) which charge 0.010.01 per GB.
Choosing the correct endpoint type minimizes data transfer costs.
3
Determine the implementation requirements for Gateway VPC endpoints.
Gateway endpoints update route tables with a prefix list destination pointing to the gateway. They do not use Elastic Network Interfaces (ENIs).
Ensuring the configuration is valid so that traffic is successfully routed over the private connection.

Key Concept

Gateway VPC endpoints provide free, direct private connectivity to DynamoDB and S3, bypassing NAT Gateways and Transit Gateways to eliminate processing fees.
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Topics

Data Transfer Cost Optimization

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