<type name="Magento\Webapi\Controller\Rest">
    <plugin name="webapiContorllerRestAsync"
            type="Magento\WebapiAsync\Plugin\ControllerRest"></plugin>
</type>

This is a type configuration.

This configuration is for the base area. Base area configurations will apply to all the sub-applications.

This configuration also tells the object manager to use the Magento\WebapiAsync\Plugin\ControllerRest plugin class with Magento\Webapi\Controller\Rest objects.