Integrating MongoDB metrices with Cloud watch
As per @AndrewAslinger blog here The Amazon CloudWatch is a useful tool for monitoring your compute resources, services, and applications running in AWS. Amazon automatically publishes metrics for you when you use many different AWS Services.

As aws documentation here Amazon CloudWatch is basically a metrics repository. An AWS service—such as Amazon EC2—puts metrics into the repository, and you retrieve statistics based on those metrics. If you put your own custom metrics into the repository, you can retrieve statistics on these metrics as well.

You can configure alarm actions to stop, start, or terminate an Amazon EC2 instance when certain criteria are met. In addition, you can create alarms that initiate Amazon EC2 Auto Scaling and Amazon Simple Notification Service (Amazon SNS) actions on your behalf. For more information about creating CloudWatch alarms, see Alarms.

For further your ref here, here and here