A company operates many EC2 instances and needs to alert the operations team whenever any instance changes state (for example, starts or stops). Which approach is the most operationally efficient to meet this requirement?

The most operationally efficient approach is to use Amazon EventBridge. EventBridge natively integrates with AWS services and can directly detect EC2 instance state-change events. By configuring an Amazon SNS topic as the target, EventBridge automatically publishes these events to the topic, which can then notify the operations team. This solution requires minimal configuration and no custom code or infrastructure management. Writing a script and using Systems Manager Run Command is less efficient because it requires managing scripts on each instance, which adds overhead and complexity. Creating an EventBridge rule to trigger a Lambda function that then publishes to SNS adds an unnecessary layer of complexity and cost (Lambda invocations) when EventBridge can directly publish to SNS. AWS Config is primarily for evaluating resource compliance and changes against desired configurations, not for real-time operational alerts on state changes, making it an overly complex solution for this specific requirement.