Your public website uses an Application Load Balancer and an Auto Scaling group in a virtual private cloud. Your chief security officer has asked you to set up a monitoring system that quickly detects and alerts your team when a large sudden traffic increase occurs. How should you set this up?

Answer options:

A.Set up an Amazon CloudWatch alarm for the Elastic Load Balancing NetworkOut metric and then use Amazon SNS to alert your team.
B.Use an Amazon EMR job to run every thirty minutes, analyze the Elastic Load Balancing access logs in a batch manner to detect a sharp increase in traffic and then use the Amazon Simple Email Service to alert your team.
C.Use an Amazon EMR job to run every thirty minutes analyze the CloudWatch logs from your application Amazon EC2 instances in a batch manner to detect a sharp increase in traffic and then use the Amazon SNS SMS notification to alert your team.
D.Set up an Amazon Cloudwatch alarm for the NetworkIn metric associated with the EC2 instances of the Auto Scaling group and then use Amazon SNS to alert your team.
E.Set up a cron job to actively monitor the AWS CloudTrail logs for increased traffic and use Amazon SNS to alert your team.

Answer - D
The below snapshot from the AWS documentation gives details on the NetworkIn metric
Please note that Application Load Balancer does not have the NetworkOut metric in CloudWatch so option A is incorrect.
For more information on EC2 metrics, please visit the link:
http://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/ec2-metricscollected.html