Why Meta’s new GEM engine is 4x more efficient at ranking ads than anything we used in 2024?

TL;DR: Andromeda loves the "Might Engage" pool; GEM picks the "Will Convert" winners. Stop overthinking the targeting.

I’ve been obsessed with the shift in ad delivery lately, specifically, how Andromeda handles the millisecond-retrieval for relevance while GEM handles the long-term pattern prediction for the actual conversion.

The efficiency gain is wild. We’re seeing a 15-25% ROAS lift just by consolidating accounts and letting the LMMs (Large Multimodal Models) do the heavy lifting. It feels like the era of "hacking the algorithm" is finally dead, replaced by "feeding the engine."

I broke down the exact flow from Retrieval to Auction in this article for anyone trying to hit their 2026 KPIs.

https://www.linkedin.com/pulse/andromeda-vs-gem-differences-ad-delivery-harshielha-balasubramanian-nve8c