# Fleet metrics
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Fleet metrics is a feature of [fleet indexing](iot-indexing.md), a managed service that allows you to index, search, and aggregate your devices' data in Amazon IoT. You can use fleet metrics, to monitor your fleet devices' aggregate state in [CloudWatch](https://console.aws.amazon.com/cloudwatch/) over time, including reviewing your fleet devices' disconnection rate or average battery level changes of a specified period.

Using fleet metrics, you can build [aggregation queries](index-aggregate.md) whose results are continually emitted to [CloudWatch](https://console.aws.amazon.com/cloudwatch/) as metrics for analyzing trends and creating alarms. For your monitoring tasks, you can specify the aggregation queries of different aggregation types (**Statistics**, **Cardinality**, and **Percentile**). You can save all of your aggregation queries to create fleet metrics for reuse in the future.