The correct answer is Set up a VPC peering connection between the VPCs in Account Alpha and Account Beta.

VPC peering is a networking connection between two VPCs that enables traffic to route privately between them using private IP addresses. It is designed to be both secure and highly available, as it does not depend on a gateway, VPN, or physical device, which eliminates any single point of failure. Additionally, VPC peering supports high-bandwidth traffic because it leverages the AWS global network backbone without throttling like some other VPN-based solutions.

Lets examine why the other choices are incorrect:

Set up VPC gateway endpoints for the EC2 instance in Account Beta is not valid in this scenario. Gateway endpoints are used to connect to AWS services like S3 or DynamoDB, not to connect two EC2 instances across VPCs.

Attach a virtual private gateway to VPC-B and configure routes from VPC-A describes a VPN-like architecture, which typically involves a customer gateway and is more appropriate for connecting on-premises networks to AWSnot for connecting two AWS-managed VPCs across accounts.

Create a private virtual interface (VIF) for the EC2 instance in VPC-B and add routes from VPC-A refers to Direct Connect configurations, which are usually employed for high-throughput, low-latency connections between AWS and on-premises networks. Using a private VIF for EC2-to-EC2 communication across VPCs within AWS is overkill and more complex than necessary.

Why this question is important: It assesses the candidate's understanding of cross-account VPC connectivity strategies, and specifically whether they can distinguish between use cases for VPC peering, Direct Connect, VPNs, and gateway endpoints. A good strategy for answering questions like this is to focus on the use case (VPC-to-VPC, secure, scalable, AWS-internal) and match it with the simplest AWS-native solution that meets the technical and operational constraints.

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