How to Design Backward Compatible APIs in .NET, Real Lessons and Tips from Production

The author discusses the importance of backward compatibility in API design to avoid breaking existing integrations. Breaking changes are costly and can disrupt entire teams, so careful design is crucial. Instead of breaking changes, developers should add, not rename, fields to maintain compatibility. Versioning should be used sparingly, reserved for significant breaking changes. The author's team learned from mistakes made while evolving an Orders API, using specific principles. They focused on not breaking existing contracts silently and providing adequate communication. Adding new functionality and changes to enums must be handled defensively to minimize disruption. New fields should be optional to avoid causing errors for older clients. Deprecation needs to be communicated early and often to users of the API. The article provides practical takeaways for managing API evolution effectively. The key is to prioritize additive changes and robust communication. The author highlights key strategies like using obsolete attributes and defensive parsing of enum values. The emphasis is on maintaining service stability and client satisfaction by carefully considering the impact of any changes.