Scaling Elixir's Flow for Massive Message Processing

John Mertens, a principal engineer at Change.org, shares insights from the practical application of Elixir, particularly using GenStage and Flow for building a high-volume, mission-critical data processing system. Mertens explains that while their stack primarily includes Ruby and JavaScript, they tapped into Elixir in early 2018 because of its concurrency features and the Flow library, which was a great fit for their problem space. He articulates lessons learned from processing a considerable volume of messages, emphasizing the importance of parallelism, backpressure, and maintaining simplicity and organization within your Flow. These concepts are critical for scalability and reliable system performance. The talk also stresses the value of understanding your entire system, including dependent services and external systems like Amazon SQS for queueing. Additionally, Mertens details the structure of their Flow, how they manage errors, isolate side effects, and optimize their process. The principle of knowing the intricacies of your code and system allows one to better structure, reason about, and optimize the operations within Elixir's Flow.