Over the years, we've built multiple backend systems that have mobile apps as one of the user-facing interfaces. We've also seen numerous backend systems where mobile developers were an afterthought. In this blog, we will discuss the importance of designing backend APIs with a mobile-first approach and how this improves the overall system design.

Understanding "Roll-Back" vs. "Roll-Forward"
Before delving deeper, it's crucial to understand the concepts of "roll-back" and "roll-forward".
Roll-back: Returning the system to a previous state or deployment.
Roll-forward (or patch): Fixing an underlying problem with a new release instead of reverting to a previous state.
As a software developer, you'll often encounter scenarios where a "roll-back" or "roll-forward" is necessary to address production issues.
Mobile Development Dynamics
Currently, iOS and Android dominate the mobile operating system market. Both platforms provide their respective stores (App Store for iOS and Play Store for Android) for downloading and updating mobile apps. In these stores, the release cycle only allows for "roll-forward" updates. There is no option to "roll-back" a release. If you discover issues with your latest release, you must submit a new build with a new version number to replace the problematic one.
For example, if you release v1.0.0 of your mobile app and then release v1.0.1, but find it crashes on launch, you can't simply revert to v1.0.0. Instead, you must submit a new version, v1.0.2, containing the v1.0.0 code.
Mobile-First Backend Design
Imagine you release v1.0.0 of your mobile app, and everything works fine. You then introduce an API change that removes a field the app expects, causing the app to crash. You submit a new build, v1.0.1, to the stores to handle this issue. However, your analytics show that users still experience crashes. This can happen because users may have turned off automatic app updates, meaning they are still using the problematic version. Another aspect to be aware of is that both the stores have a review cycle which means that the users may not have access to the new build for potentially a few days even once you submit your builds.
If most of your users have disabled automatic updates, the app remains useless for them, continually crashing. The only way to resolve this is to perform a "roll-back" on your API.
The Amplified Challenge with Mobile SDKs
This problem is exacerbated if you provide a mobile SDK that other apps consume. In this case, there's an additional layer of delay: your SDK consumers need to update their app with the new SDK version and then submit a release, hoping their users update it. This adds significant lag in addressing issues. This is significantly different from web development where you could update the client code and on the next refresh / fetch, the patch gets applied.
The Importance of Semantic Versioning
To handle these challenges, at Lastbyte Solutions, we follow Semantic Versioning principles for all APIs from day one. Here’s how we do it:
API Versioning: All our APIs are versioned.
Backward Incompatible Changes: These changes are strictly introduced with a new version update.
Maintaining Previous Versions: We maintain previous versions until most of the traffic has migrated away from them.
By following these principles, we ensure that our backend systems are resilient to changes and better equipped to handle the nuances of mobile app development.
Beyond Versioning: Best Practices for Mobile-First Backend Design
While versioning is crucial, other best practices can further enhance your backend's compatibility and performance with mobile apps:
1. Graceful Degradation
Design your APIs to degrade gracefully if certain data or features are unavailable. For example, if an API field is removed, ensure the app can handle its absence without crashing. This might involve providing default values or designing the app to check for the field's presence before using it.
2. Feature Flags
Utilize feature flags to control the rollout of new features or changes. This allows you to enable or disable features without deploying new code, providing a quick way to address issues that arise from API changes.
3. Comprehensive Testing
Ensure thorough testing of APIs with multiple versions of the mobile app. Automated tests can simulate various scenarios where older versions of the app interact with newer API versions, helping to identify potential issues before they reach production.
4. Backward Compatibility
Always aim for backward compatibility in your API changes. When deprecating features, provide ample warning and a transition period for mobile developers to update their apps. Avoid making breaking changes without a clear migration path.
5. Real-Time Monitoring and Alerts
Implement real-time monitoring and alerts for your APIs. This allows you to quickly detect issues caused by API changes and address them before they impact a large number of users.
Conclusion
Designing backend APIs with a mobile-first approach is crucial. It ensures that mobile apps remain functional and stable, even when backend changes are made. By adhering to Semantic Versioning, employing best practices such as graceful degradation, feature flags, comprehensive testing, and providing robust documentation and support, we can create a resilient system that supports seamless mobile experiences and mitigates the risks associated with updates and changes.
At Lastbyte Solutions, our commitment to these principles has enabled us to build reliable, user-friendly mobile applications that stand the test of time. By prioritizing mobile development considerations in backend design, we ensure a smoother, more efficient development process and a better overall experience for end-users.