Which AWS service should the company use to conduct the test with the LEAST amount of operational overhead?

Explanations:

Amazon EC2 requires provisioning and managing virtual servers, which increases operational overhead for this task. The application would need to handle scaling, availability, and maintenance, making it less ideal for simple image processing.

AWS CodeDeploy is a deployment service for automating application deployments. It does not inherently provide the functionality to trigger actions based on S3 events or to process images, thus making it unsuitable for this specific scenario.

AWS Lambda is a serverless computing service that automatically runs code in response to events such as S3 uploads. It requires no management of servers, making it ideal for processing images with minimal operational overhead.

Amazon Lightsail provides a simplified cloud platform with virtual servers but still requires management of instances. It does not offer the serverless architecture or event-driven capabilities needed for automatically processing images in response to S3 events.