Which AWS service can detect the total load that has exceeded the defined threshold across multiple servers and provide an alarm?

The correct choice is Amazon CloudWatch because it is specifically designed for monitoring AWS resources and applications in real-time. CloudWatch collects and tracks metrics, collects log files, and sets alarms, enabling users to create alarms based on predefined thresholds. If, for example, the total load across multiple servers exceeds the threshold set in CloudWatch, it can trigger an alarm, alerting administrators to take necessary action.

This ability to monitor and respond based on metrics is integral to maintaining health and performance across various AWS services. In the context of managing multiple servers, CloudWatch's capability to aggregate metrics and provide a holistic view is crucial.

Amazon EC2 provides infrastructure as a service but does not include built-in monitoring capabilities for setting alarms based on load thresholds. Amazon S3 is a storage service and does not inherently deal with server load monitoring. Amazon RDS, while it does have monitoring capabilities, is focused primarily on database instances and would require integration with CloudWatch to achieve comprehensive server load detection and alarm functionality. Thus, the distinguishing feature of providing alarms based on load metrics across multiple servers belongs to Amazon CloudWatch.