Which architectural change should a network engineer implement to provide the DNS service in the MOST scalable way?

A data analytics company has a 100-node high performance computing (HPC) cluster. The HPC cluster is for parallel data processing and is hosted in a VPC in the AWS Cloud. As part of the data processing workflow, the HPC cluster needs to perform several DNS queries to resolve and connect to Amazon RDS databases, Amazon S3 buckets, and on-premises data stores that are accessible through AWS Direct Connect. The HPC cluster can increase in size by five to seven times during the company’s peak event at the end of the year.

The company is using two Amazon EC2 instances as primary DNS servers for the VPC. The EC2 instances are configured to forward queries to the default VPC resolver for Amazon Route 53 hosted domains and to the on-premises DNS servers for other on-premises hosted domain names. The company notices job failures and finds that DNS queries from the HPC cluster nodes failed when the nodes tried to resolve RDS and S3 bucket endpoints.

Which architectural change should a network engineer implement to provide the DNS service in the MOST scalable way?
A . Scale out the DNS service by adding two additional EC2 instances in the VPC. Reconfigure half of the HPC cluster nodes to use these new DNS servers. Plan to scale out by adding additional EC2 instance-based DNS servers in the future as the HPC cluster size grows.
B. Scale up the existing EC2 instances that the company is using as DNS servers. Change the instance size to the largest possible instance size to accommodate the current DNS load and the anticipated load in the future.
C. Create Route 53 Resolver outbound endpoints. Create Route 53 Resolver rules to forward queries to on-premises DNS servers for on premises hosted domain names. Reconfigure the HPC cluster nodes to use the default VPC resolver instead of the EC2 instance-based DNS servers. Terminate the EC2 instances.
D. Create Route 53 Resolver inbound endpoints. Create rules on the on-premises DNS servers to forward queries to the default VPC resolver. Reconfigure the HPC cluster nodes to forward all DNS queries to the on-premises DNS servers. Terminate the EC2 instances.

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Answer: C