https://aws.amazon.com/migration-evaluator/features/

This solution requires the least amount of effort as it only requires to update the API endpoint to private in API Gateway and create an interface VPC endpoint. Then create a resource policy and attach it to the API. This will make the API only accessible from the VPC and still keep the authentication mechanism intact. Reference:
https://aws.amazon.com/premiumsupport/knowledge-center/private-api-gateway-vpc-endpoint/
https://aws.amazon.com/api-gateway/features/

AWS Organizations is a service that enables you to consolidate multiple AWS accounts into an organization that you create and centrally manage. By creating a management account and inviting all the existing accounts to join the organization, the solutions architect can track and consolidate expenditures for all the accounts using AWS Cost Management tools such as AWS Cost Explorer and AWS Budgets. An organizational unit (OU) is a group of accounts within an organization that can be used to apply policies and simplify management. A service control policy (SCP) is a type of policy that you can use to manage permissions in your organization. By creating an OU that includes all the development teams and applying an SCP that allows the creation of resources only in Regions that are in the United States, the solutions architect can ensure that the company meets its compliance requirements and avoids unwanted charges from other Regions. An IAM role is an identity with permission policies that determine what the identity can and cannot do in AWS. By creating an IAM role in the management account and allowing the finance team users to assume it, the solutions architect can give them access to view the Billing and Cost Management console without sharing credentials or creating additional users. Reference:
https://docs.aws.amazon.com/organizations/latest/userguide/orgs_introduction.html
https://docs.aws.amazon.com/organizations/latest/userguide/orgs_manage_policies_scp.html
https://docs.aws.amazon.com/IAM/latest/UserGuide/id_roles.html
https://docs.aws.amazon.com/aws-cost-management/latest/userguide/what-is-costmanagement.html

Updating the ingestion process to use Amazon Kinesis Data Firehose to save data to Amazon S3 will reduce the need for EC2 instances and EBS volumes for data storage1. Using AWS Batch with Spot Instances to perform nightly processing will leverage the cost savings of Spot Instances, which are up to 90% cheaper than On-Demand Instances2. AWS Batch will also handle the scheduling and scaling of the processing jobs. Setting the maximum Spot price to 50% of the On-Demand price will reduce the chances of interruption and ensure that the processing is cost-effective.

https://docs.aws.amazon.com/application-discovery/latest/userguide/discovery-agent.html https://docs.aws.amazon.com/migrationhub/latest/ug/ec2-recommendations.html