GenPage: Towards End-to-End Generative Homepage Construction at Netflix
GenPage is Netflix’s end-to-end generative approach to building personalized homepages. Instead of separately ranking rows and items, one transformer autoregressively generates the entire page—including rows, entities, and layout—from user and request context. In production, it outperformed Netflix’s mature multi-stage recommender on a core engagement metric while reducing serving latency by 20%. ## Reframing Homepage Recommendation - Netflix’s homepage is a personalized two-dimensional structure, not a single ranked list. - Traditional systems use separate candidate-generation and ranking stages for rows and entities. - GenPage treats homepage construction as a prompt-response task: - The prompt contains user history, profile information, and request context. - The response is the complete homepage generated autoregressively. - The approach aims to: - Replace complex multi-stage pipelines with one end-to-end model. - Optimize the whole page using reinforcement learning. - Capture interactions such as diversity and the trade-off between high-value rows and continued browsing. - Scale more predictably with additional data, compute, and model capacity. - Support new content types, layouts, UI components, and personalized artwork with fewer architectural changes. ## Production Challenges and Results - Real-time generation makes serving latency a major constraint. - The system must address: - Cold-start entities in a constantly changing catalog. - Shifting user interests and cultural trends. - Product and business rules that constrain generated pages. - An online A/B test against Netflix’s optimized production recommender produced: - Statistically significant improvement on Netflix’s primary launch engagement metric. - A 20% reduction in end-to-end serving latency. - Offline experiments found that: - Improving the prompt helped more than increasing model capacity in the tested regime. - Reinforcement-learning post-training improved homepage diversity, even though diversity was not an explicit objective. ## Tokenizing Context and Pages - Each training example contains: - **Context:** user history, profile attributes, and request information. - **Page:** displayed rows and entities in layout order. - **Feedback:** interactions such as plays, thumbs-up, and abandonment. - Context and page are tokenized as model inputs and outputs. - Feedback is used to derive reward and supervision signals rather than being directly generated. ## Domain-Specific Tokenization - GenPage uses a custom recommender-system tokenizer instead of a general-purpose text tokenizer. - This reduces sequence length and improves inference cost and latency. - For example, an action such as watching *Orange Is the New Black* can be represented with four tokens: - Entity ID - Action type - Time bucket - Duration bucket - Direct token mappings to product concepts, such as rows and entities, also make it easier to enforce generation rules and business constraints. ## Context Representation - User-history tokens encode: - Action type - Entity ID - Timestamp - Duration - The history includes explicit signals, such as playback, adding titles to My List, and thumbs-up, as well as implicit signals such as trailer views and detail-page visits. - Profile tokens represent attributes including language and profile type. - Request-context tokens include time of day, day of week, and device. - Long data sources, such as complete impression histories, are summarized to control sequence length and cost. - These summaries improve practicality but introduce handcrafted prompt engineering; learning to compress such information end to end remains a future direction. - Special segment markers help the model distinguish between different context sources.
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