This document discusses Hadoop and big data at LinkedIn. It provides an overview of LinkedIn's data infrastructure, which includes various technologies like Hadoop, HBase, and messaging systems. Hadoop is used for recommendations, data warehousing, and data science projects at LinkedIn. Some challenges of using Hadoop include user adoption of new technologies, enabling real-time processing, handling graph algorithms, and making large datasets accessible. The presentation concludes by emphasizing that Hadoop is best for offline processing while other technologies may be needed for real-time use cases.