The primary requirement is to find the lowest-cost solution for high-volume data transfer between VPCs. VPC Peering offers the most cost-effective data transfer rates. Data transferred over a VPC peering connection within the same Availability Zone (AZ) is free. By using the zonal DNS names of the Network Load Balancers (NLBs) in the services VPCs, the front-end application can explicitly send traffic to the NLB node located in the same AZ as the source pod. This strategy eliminates cross-AZ data transfer charges, which would be substantial given the 10 TB of monthly traffic. This makes VPC Peering the most economical choice compared to AWS Transit Gateway or AWS PrivateLink, both of which incur mandatory data processing fees regardless of the AZ.

A. A transit gateway incurs a data processing fee of $0.02 per GB, which is double the cost of cross-AZ VPC peering and significantly more expensive than same-AZ peering (which is free).

B. AWS PrivateLink has hourly costs for each VPC endpoint in each AZ, in addition to a data processing fee of $0.01 per GB. This makes it more expensive than the free same-AZ VPC peering option.

D. A transit gateway is inherently more expensive for data processing. Using Regional DNS names would distribute traffic across all AZs, guaranteeing cross-AZ data transfer costs, which contradicts the goal of minimizing cost.

1. Amazon EC2 On-Demand Pricing - Data Transfer: Under the "Data Transfer" section, it specifies the costs for data transfer via "Amazon VPC Peering". It explicitly states that for traffic within the same AWS Region, data transfer within the "Same Availability Zone" is "$0.00 per GB". Data transfer to a "Different Availability Zone" is "$0.01 per GB". This confirms that keeping traffic in the same AZ via peering is free. (Source: Official AWS EC2 Pricing Documentation).

2. AWS Transit Gateway Pricing: This page details that Transit Gateway has a "$0.02 per GB of data processed" fee, in addition to hourly attachment costs. This is demonstrably more expensive than the VPC peering model for this use case. (Source: Official AWS Transit Gateway Pricing Documentation).

3. AWS PrivateLink Pricing: This page shows that PrivateLink has a "$0.01 per GB for data processed" fee and an hourly charge for each VPC Endpoint. The combination of these costs makes it more expensive than same-AZ VPC peering. (Source: Official AWS PrivateLink Pricing Documentation).

4. Elastic Load Balancing User Guide - Load balancer DNS names: The documentation for Network Load Balancers states: "For each Availability Zone that you enable for your load balancer, the load balancer node in that zone uses a zonal DNS name... If you need to target a load balancer node in a specific zone, you can use its zonal DNS name." This confirms the technical validity of the strategy proposed in the correct answer. (Source: AWS Elastic Load Balancing User Guide, section on DNS names).