It’s designed for omnipresent surveillance of all of the cells, in such a manner that the people in the cells can’t tell if or when they’re being directly surveilled, such that a single guard can provide surveillance to an entire prison. It’s supposed to be a method of self/surveillance, as those in the cells never know when they’re being surveilled they act as though they always are. It’s a chilling metaphor for modern surveillance and capitalism and the irony becomes even more ironic given that this is Amazon who’s decided that they need to observe all their employees all the time.