That could be a fun programming exercise for one of these devices you can hook into Alexa, see if you can catch unauthorised voices quickly and effectively with

That could be a fun programming exercise for one of these devices you can hook into Alexa, see if you can catch unauthorised voices quickly and effectively without badly impacting response times. e.g. you could do it by buffering the request, checking and submitting once you're confident about authenticity, but then you'd be delaying submission and response, depending on how much you'd need to buffer to gain sufficient confidence that the individual is authorised.