One of the most enigmatic characters in the movie is Joi, K's computerized virtual girlfriend. Since she was created by Wallace, it's implied that she might be a true AI—after all, that's what the replicants are too in a sense, only in manufactured human bodies. Or maybe she isn't? The mass marketing of identical Joi, right down to calling their partners "Joe," suggests that she might just be a sophisticated program designed to emulate human emotion. Did she really love K, or was she just programmed to act that way?
It matters in part because of the other big question about Joi: why and how did she end up contacting Mariette for that incredibly disturbing sex scene? Was she truly doing it because she wanted to experience sex with K in a physical form? Or was there something else going on with her programming? It's more than coincidence that she happened to contact a member of the replicant resistance who's been ordered to keep tabs on K. Did the resistance somehow hack Joi, or was she programmed to help them all along? It's a little odd that she disappears just long enough for Mariette to put the tracker on K, especially considering she doesn't exactly have anywhere else to go.
All in all, it seems like there's more than meets the eye to Joi. Exactly what, though, is anyone's guess.