Sona: one transformer replaced our 15+ candidate generators, pre-ranker and ranker in an A/B test [R]

Yandex Music developed Sona, a single transformer model that replaced over 15 candidate generators, a pre-ranker, and a ranker in an A/B test. Sona processes up to 8,192 events using a History Compression technique to reduce inference costs by roughly half. This method involves splitting event history into two blocks (6,144 older and 2,048 recent events) that exchange information via cross-attention and a full-history self-attention layer, followed by a 7-layer stack on the recent events.

This report details how a single transformer model replaced 15+ components in an A/B test, unlike previous multi-component recommender systems.