A finance company uses Amazon Redshift as a data warehouse. The company stores the data in a shared Amazon S3 bucket. The company uses Amazon Redshift Spectrum to access the data that is stored in…

Placing the Amazon Redshift cluster in a private subnet ensures that the cluster's network interfaces are not directly accessible from the public internet, thereby preventing unauthorized external access to the Redshift data warehouse.

AWS CloudHSM is a service for managing cryptographic keys within hardware security modules; it does not directly control network access or prevent data from being accessible outside the AWS environment.

Enabling enhanced VPC routing forces all Redshift traffic (including S3 and Redshift Spectrum traffic) to pass through the customer's VPC, and combining this with an AWS Direct Connect connection provides a dedicated, private network path from on-premises to AWS, completely bypassing the public internet for data access.

Defining primary and foreign key constraints enforces data integrity within the Redshift database but has no impact on controlling network access or preventing data exposure outside the AWS environment.

Federated queries allow Redshift to query data in external databases (like RDS or other Redshift clusters); this does not restrict access to the Redshift data or the S3 data from outside the AWS environment.