A company wants to migrate its web application to AWS and leverage auto scaling to...

Concurrent users is an application-level metric, not a default infrastructure metric. CloudWatch provides standard metrics such as CPU utilization, network input, and request counts for many AWS services, but it will not automatically know how many active users the application currently has unless the application publishes that value. The correct design is to publish concurrent user count as a custom CloudWatch metric and use that metric in the scaling policy. SNS is a notification service, not a metric source. CloudFront can improve content delivery, but it does not directly define application auto scaling based on concurrent users. NetworkIn might correlate with load but is not the metric chosen by the architect. CloudWatch supports custom metrics and alarms for threshold-based actions. ( AWS Documentation )

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