If you’re curious about how we used ensembled weak learners to form a strong enough learner to kick the shit out of everyone except DoubleClick in AdTech, this is a decent start: https://en.m.wikipedia.org/wiki/Ensemble_learning.

By the standards of AdTech, latent space stuff was pretty unproven when I left the game a few years ago.

Low-rank approximations were in some sense implicit in that, but were not at that time an explicit goal.

If I were doing an AdTech system from scratch I’d most likely reach for the kind of recommender systems that you’re alluding to sooner.

Sounds like you know your stuff :)