Event Schema Evolution: Backward and Forward Compatibility in Event-Driven Systems

Short summary

Part 3 of a series on reliable event-driven systems, focusing on event schema evolution and versioning. The article argues compatibility matters more than version numbers: backward compatibility lets old consumers handle new events safely (add optional fields, don't remove fields), while forward compatibility requires new consumers to gracefully handle missing fields from older producers. Real-world examples show how replacing a field breaks all downstream consumers.

• •Event schemas inevitably change as systems grow; compatibility matters more than version numbers
• •Backward compatibility: add optional fields, never remove or rename existing ones
• •Forward compatibility: consumers must handle missing fields with defaults or fallback logic

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