In this paper, we present LiGNN, a deployed large-scale Graph Neural Networks (GNNs) Framework. We share our insight on developing and deployment of GNNs at large scale at LinkedIn. We present a set of algorithmic improvements to the quality of GNN representation learning including temporal graph architectures with long term losses, effective cold start solutions via graph densification, ID embeddings and multi-hop neighbor sampling. We explain how we built and sped up by 7x our large-scale training on LinkedIn graphs with adaptive sampling of neighbors, grouping and slicing of training data batches, specialized shared-memory queue and local gradient optimization. We summarize our deployment lessons and learnings gathered from A/B test experiments. The techniques presented in this work have contributed to an approximate relative improvements of 1% of Job application hearing back rate, 2% Ads CTR lift, 0.5% of Feed engaged daily active users, 0.2% session lift and 0.1% weekly active user lift from people recommendation. We believe that this work can provide practical solutions and insights for engineers who are interested in applying Graph neural networks at large scale.

User experience at social media and web platforms such as LinkedIn is heavily dependent on the performance and scalability of its products. Applications such as personalized search and recommendations require real-time scoring of millions of structured candidate documents associated with each query, with strict latency constraints. In such applications, the query incorporates the context of the user (in addition to search keywords if present), and hence can become very large, comprising of thousands of Boolean clauses over hundreds of document attributes. Consequently, candidate selection techniques need to be applied since it is infeasible to retrieve and score all matching documents from the underlying inverted index. We propose CaSMoS, a machine learned candidate selection framework that makes use of Weighted AND (WAND) query. Our framework is designed to prune irrelevant documents and retrieve documents that are likely to be part of the top-k results for the query. We apply a constrained feature selection algorithm to learn positive weights for feature combinations that are used as part of the weighted candidate selection query. We have implemented and deployed this system to be executed in real time using LinkedIn's Galene search platform. We perform extensive evaluation with different training data approaches and parameter settings, and investigate the scalability of the proposed candidate selection model. Our deployment of this system as part of LinkedIn's job recommendation engine has resulted in significant reduction in latency (up to 25%) without sacrificing the quality of the retrieved results, thereby paving the way for more sophisticated scoring models.