What to do if you need to break backward compatibility (for example, by adding a mandatory field)?

If it is necessary to break backward compatibility, for example, by adding a mandatory field, it is important to act carefully to minimize risks:

1. API or data schema versioning. Create a new version where the mandatory field is added, and the old version remains unchanged.
2. Gradual transition. Introduce the new field as optional, collect data, then make it mandatory in the next release.
3. Client and documentation updates. Inform users about upcoming changes and give them time to adapt.
4. Testing. Conduct thorough testing of the new version to avoid failures.

This approach allows existing clients to continue working and gradually implement changes without abrupt failures.