Pinterest's home feed personalization process involves retrieving candidate pins based on user interests and ranking them using the Pinnability model.
TransActV2, an upgraded model, addresses the limitation of not being able to model a user's lifelong behavior on Pinterest.
TransActV2 leverages long user sequences, a Next Action Loss function, and efficient deployment solutions.
It aims to capture evolving user interests, provide rich personalization, and handle the challenges of processing extensive user histories.
The model can now handle up to 16,000 user actions and includes features like timestamp, action type, action surface, and PinSage embeddings.
Nearest Neighbor Selection is used to reduce the length of user sequences during ranking, improving efficiency.
The model architecture involves representation layers, a Transformer Encoder, and downstream heads for various action predictions.
Next Action Loss (NAL) is introduced to enhance action forecasting by predicting the user's next action given the context and history.
Efficient serving and deployment strategies like Nearest Neighbor feature logging and custom Triton kernels are implemented to handle lifelong sequences.
TransActV2's improvements led to significant enhancements in offline metrics and user engagement, outperforming prior systems.
Real-world A/B tests showed substantial increases in repins, reduced hide signals, improved session quality, and enhanced content diversity.