Explore streaming data processing in Scala and the Lightbend Reactive platform through this 47-minute conference talk from Scala Days Berlin 2016. Dive into the advantages and concepts of streaming data processing, focusing on Akka Persistence Query and its implementation in the Cassandra plugin for Akka Persistence. Examine architecture and design considerations, implementation details, performance tuning, and distributed system specifics such as correctness, efficiency, consistency, order, causality, and failure scenario handling. Learn about improvements to the Cassandra plugin, including non-blocking asynchronous Akka Persistence recovery, and discover how to apply these concepts to build modern reactive enterprise stream processing and asynchronous messaging distributed applications. Cover topics like data at scale, streams, log data structures, event time processing, distributed causal stream merging, exactly once delivery, and challenges in distributed systems.