period

The length, in seconds, used each time the metric specified in MetricName is evaluated. Valid values are 10, 20, 30, and any multiple of 60.

Period is required for alarms based on static thresholds. If you are creating an alarm based on a metric math expression, you specify the period for each metric within the objects in the Metrics array.

Be sure to specify 10, 20, or 30 only for metrics that are stored by a PutMetricData call with a StorageResolution of 1. If you specify a period of 10, 20, or 30 for a metric that does not have sub-minute resolution, the alarm still attempts to gather data at the period rate that you specify. In this case, it does not receive data for the attempts that do not correspond to a one-minute data resolution, and the alarm might often lapse into INSUFFICENT_DATA status. Specifying 10, 20, or 30 also sets this alarm as a high-resolution alarm, which has a higher charge than other alarms. For more information about pricing, see Amazon CloudWatch Pricing.

An alarm's total current evaluation period can be no longer than seven days, so Period multiplied by EvaluationPeriods can't be more than 604,800 seconds. For alarms with a period of less than one hour (3,600 seconds), the total evaluation period can't be longer than one day (86,400 seconds).