Metrics

Metrics are a core component of CloudWatch. They are used to monitor AWS resources and our applications, and can be configured to react accordingly using CloudWatch alarms. Every AWS resource generates metrics at regular intervals, and we can also store custom metrics generated from our application. For example, our application is failing because of a database connection error and we generate metrics and store them on CloudWatch Metrics. For this database connection error metrics we created CloudWatch alarms when the number of errors crosses certain threshold, generate email notification to the group of people using SNS. So in this way we can use custom metrics as well as AWS resources metrics.   

Metrics generated in a specific region can be used in that region only. We can't delete the metrics and data points. CloudWatch deletes metrics automatically after 15 months if no new data points are added under the metrics. And as data points are added under the metrics, 15-month-old data...