As convenient as Amazon's in-home delivery can be, the app powering it isn't entirely secure. It normally grants full access to your smart lock and camera footage, which would pose a rather obvious problem if the wrong person had one of your mobile devices. As of now, though, you can throw an obstacle in their way: the Amazon Key app for Android now supports fingerprint authentication. Switch it on and you should be the only one who can open the door.
There's no mention of a corresponding iOS update so far. The upgrade acknowledges a reality of services like this, however. You're putting a whole lot of trust in Key and its app, and that makes security particularly important -- a vulnerability could lead to people having direct access to your home.