In some of the Yggdrasil Outposts, there are a wall of lockers with doors in both front and back. The front faces a “locker room” where someone with a key code (or wallet signature) is able to unlock a locker and retrieve its contents without human intervention.
The other side is inside a protected room, and it gives a Grocer space and privacy to do the appropriate transfers to stock the shelves.
Rhinegold is the software which manages access to the lockers which have electronic locks on both doors. It is receiving instructions on who owns what from Jörmungandr, recalling that the Couriers and Grocer are both blind to the contents of the package, and only have access to the shipping identifier.