The key in the usage event payload to use as the value for this meter. For example, if the event payload contains usage on a bytes_used field, then set the event_payload_key to "bytes_used".
bytes_used
The key in the usage event payload to use as the value for this meter. For example, if the event payload contains usage on a
bytes_usedfield, then set the event_payload_key to "bytes_used".