Event-Driven Architecture Patterns

Command-style communication tells another service what to do: create an order, charge a card, or reserve stock. It is easy to follow, but tightly couples each service to the next.

Event-driven architecture flips this. A service publishes what happened, such as OrderPlaced, and any interested service reacts independently.

This reduces direct coupling, but event design matters.

This chapter covers common event patterns, what each event should contain, their trade-offs, and the consistency challenges in event-driven systems.