Lattice is the ranking and auction layer in Meta's AI ad-serving stack, scoring and pricing the ad shortlist that Andromeda's retrieval pass hands it for each impression.
Lattice sits downstream of Andromeda in Meta's delivery pipeline. Andromeda does the retrieval work first, sweeping billions of candidate ads down to a manageable shortlist for a given impression. Lattice takes that shortlist and runs the ranking and auction pass: it scores each candidate on bid, predicted action rate and ad quality, then prices the winning impression.
GEM (Generative Engagement Model) feeds engagement-prediction signals into this pass, so Lattice isn't scoring on bid alone — it's weighing how likely a specific viewer is to engage with a specific creative before it sets a price. The practical effect is that a lower bid with stronger predicted engagement can out-auction a higher bid with a flatter one.
Every Meta advertiser's ads pass through Lattice, whether or not they've opted into Advantage+ Audience or Advantage+ Creative. It's infrastructure, not a toggle.
Lattice is why creative quality shows up in auction pricing, not just bid amount. Campaigns with weak predicted-engagement creative pay more to win the same impression a stronger creative would win cheaper — the auction is penalizing the ad, not just rewarding the highest bidder.
