AWS Certified Solutions Architect Professional SAP-C02 Practice Question
A company operates two VPCs in the us-east-1 Region.
The Service VPC hosts a REST API behind a Network Load Balancer deployed in two Availability Zones (AZs).
The Consumer VPC runs an Auto Scaling group in two other AZs that invokes the API continuously.
The VPCs are connected by VPC peering. VPC Flow Logs show about 6 TiB of traffic in each direction every day, and more than 90 percent of this traffic crosses AZ boundaries.
The monthly AWS bill lists roughly US $7,200 for "USE1-VpcPeering-In-Bytes" and "USE1-VpcPeering-Out-Bytes" (US $0.01 per GiB for each direction).
The CFO asks the solutions architect to cut this data-transfer cost by at least 40 percent without exposing the traffic to the public internet or reducing workload availability. The networking team prefers a solution that avoids per-VPC route-table edits.
Which change will meet the requirements?
Enable cross-zone load balancing on the Network Load Balancer so requests remain in one Availability Zone.
Expose the REST API as an AWS PrivateLink endpoint service and create interface VPC endpoints in the Consumer VPC.
Delete the VPC-peering connection and establish two Site-to-Site VPN tunnels over the internet between the VPCs.
Attach both VPCs to an AWS Transit Gateway and remove the VPC-peering connection.
Traffic sent across an inter-AZ VPC-peering connection is billed twice-US $0.01 per GiB for the egress side and US $0.01 per GiB for the ingress side-so the effective rate is US $0.02 per GiB.
Publishing the API as an AWS PrivateLink endpoint service and creating interface VPC endpoints in the Consumer VPC keeps the traffic on the AWS backbone and makes inter-AZ data transfer free for PrivateLink. The traffic is charged a single US $0.01 per GiB data-processing fee on the total data volume, cutting the per-GiB cost roughly in half and meeting the 40 percent savings target; hourly endpoint charges are minor relative to the transfer savings. No route-table changes are needed because Interface Endpoints use elastic network interfaces inside the Consumer VPC.
AWS Transit Gateway would add a US $0.02 per GiB data-processing fee plus attachment hours, which would not result in savings. Enabling cross-zone load balancing does not address the cost of data transfer between VPCs and often increases cross-AZ transfers within the load balancer's VPC. Using Site-to-Site VPN over the internet would introduce higher internet egress charges and additional operational overhead.
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AWS Certified Solutions Architect Professional SAP-C02
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