Design Patterns for Cloud Native Applications

Chapter 6. Stream-Processing Patterns

Stream-processing patterns evolved from event-driven architecture patterns. Event-driven architecture patterns revolve around event delivery and orchestration, whereas stream-processing patterns focus on how such events can be processed on the fly to extract meaningful information and take actions in real time. Without event-driven architecture patterns, we cannot implement stream-processing patterns in cloud native systems.

What Is a Stream?

A stream can be defined as a continuous sequence of events ordered by time. The stream consists of a name and version that uniquely identify it, such as StockStream 1.0. All events in a stream have a common message format and structure. For example, StockStream has a JSON format and contains symbol, price, and volume in its structure. Having a consistent format and structure allows events in the stream to be processed in an automated manner, using stream-processing systems. The stream version provides a way to safely modify the structure and evolve the stream over time.

What Is Stream Processing?

Stream processing is performing operations on events in motion. It can be as simple as a stateless service consuming events and transforming its event format, or as complex as storing and processing stateful data in memory with low latency and reliability.

In contrast to simple event processing, stream processing supports use cases in which events need to be handled in the order they are generated. Stream-processing ...