f you are building data pipelines for a video streaming site, you would need to consume analytics about video views in real time. Assume you need to look up additional user attributes like the subscription level, that information will change very infrequently. However, once that change happens its important to start tying usage to the correct subscription right away. So you need to find the best way to lookup that info in Apache Spark. With Delta Lake format, the batch data frame will update in memory without restarting the stream. The video in this post shows an example of this in action. Delta Lake supports updates via the merge statement so you keep the data up to date in your file system and Spark will also update its in memory data frame.