Micro Services - Backward compatibility design

Microservice Backward Compatibility

In a microservices architecture, ensuring backward compatibility is crucial for maintaining system stability and allowing independent deployment of services without breaking upstream dependencies.

One of the primary goals in a microservices architecture is to enable independent deployment of services. This means that changes to one service should not break or disrupt the functionality of other services that depend on it. To achieve this, backward compatibility must be maintained, ensuring that new changes do not affect existing contracts or interfaces. 

Here are some key approaches to achieve backward compatibility: 

Approach: Contract Models – Enhance Instead of Change

When evolving a microservice, it is important to enhance the contract models rather than changing them. This means adding new fields or endpoints instead of modifying or removing existing ones. By doing so, existing clients can continue to function without any changes, while new clients can take advantage of the enhanced features. This approach ensures that the service remains backward compatible and does not break any upstream dependencies. 

Approach: Create Adaptor

Another effective approach is to create an adaptor. Instead of changing the contract model directly, an adaptor can be introduced to handle the differences between the internal business model and the contract model. This allows the internal business model to evolve independently of the contract model. The adaptor translates between the two models, ensuring that the contract remains stable and backward compatible. This approach provides flexibility to change the internal business logic without impacting the external contract. 

Version Strategy to Communicate Major Changes

When major changes are necessary, a versioning strategy should be employed. Versioning the API allows clear communication of the contract version that the API is working with. By using version numbers in the API endpoints (e.g., /api/v1/resource), clients can explicitly specify which version of the contract they are using. This ensures that clients are aware of the changes and can migrate to the new version at their own pace, while still maintaining backward compatibility with the older versions.