Which solution meets these requirements?

Explanations:

AWS PrivateLink provides private connectivity to services across VPCs, but it is not necessary for connecting a Lambda function to a database within the same VPC. Additionally, this solution does not directly address the need for the Lambda function to be in the same network context as the database.

By connecting the Lambda function to the VPC where the database resides, the Lambda function can use the database’s private endpoint for secure access. This maintains security by ensuring that the database is not exposed to the public internet while allowing the Lambda function to communicate with it effectively.

While attaching an IAM role with read permissions is important for authorizing access, it does not address the network connectivity issue. The Lambda function must still be configured to access the database’s private endpoint within the VPC. Without network access, permissions alone will not allow the Lambda function to connect to the database.

Moving the database back to a public subnet would expose it to the public internet, which compromises security. Although security groups can help control access, this solution does not adhere to the principle of least privilege and increases the risk of exposure to attacks.