also another approach less verbose?
$.data.{
'time': %.time,
'metric': dev_intf,
'value': sent_kbps
}
https://try.jsonata.org/fsUn3LSQ_
parse-json
| jsonata "$.data.{'time': $fromMillis($number(%.time) * 1000),'metric': dev_intf,'value': sent_kbps}"
| pivot sum("value"), "time", "metric"