As companies look to streamline app development, many are migrating their native mobile apps to cross-platform frameworks like Flutter. This shift offers several advantages: faster development cycles, lower maintenance costs, and a unified experience across both Android and iOS. However, migrating a complex, production-ready app presents challenges that require a solid strategy to avoid impacting the ongoing development of a product. In this article, I’ll compare two common migration strategies —Big Bang and Incremental migration—and break down the pros and cons of each approach and explain why an incremental, flow-based migration may often be the smarter choice.
For a detailed comparison of Flutter, React Native, and Native development, check out my previous article where I explore the pros and cons of each framework.
The Big Bang approach
The Big Bang approach involves a full rewrite of your app in Flutter, offering a clean slate for revamping the architecture and user experience. It's often seen as ideal for projects needing a complete overhaul. However, this method requires halting native development during the rewrite, as engineers focus on replicating all existing features in Flutter. Once the process is complete, the goal is to release the app seamlessly, without users experiencing disruptions or loss of functionality.
The pros of the Big Bang approach
The Big Bang approach to migration offers several clear benefits for apps needing a complete overhaul:
- Fresh start: Allows you to rethink your app’s architecture from the ground up, which is useful if the current codebase has become bloated or difficult to maintain.
- Consistency: By launching a fully rebuilt app, you ensure all parts of the user experience are fully optimized for Flutter.
- Reduced legacy code: By rewriting the app, you eliminate old workarounds and platform-specific bugs, improving maintainability and performance.
The cons of the Big Bang approach
While the Big Bang approach offers benefits, it also comes with significant downsides:
- High risk: The extended development cycle can take months or even years, leaving your native app essentially frozen unless you invest additional resources into maintaining it during the rewrite.
- Long release cycle: New features and bug fixes can't be released until the Flutter app is complete, which can slow down progress for fast-moving products.
- Potential Quality Drop: Without releasing and testing small chunks of functionality, the first release of the Flutter app could introduce unforeseen bugs or performance issues.
When to consider the Big Bang approach
The Big Bang approach is suitable in specific scenarios:
• If your app is undergoing a significant transformation in its functionality or user experience (e.g., pivoting to a new purpose).
• If you're looking to start fresh and discard the majority of legacy code.
Incremental migration: a flow-based approach
The incremental migration strategy is a gradual approach where parts of the app are migrated to Flutter in stages, allowing development to continue without disrupting the entire app. Instead of rewriting the entire app at once, you focus on migrating one flow or feature at a time while keeping the rest of the app in its native form. For example, in a fintech app, you might start by migrating the money transfer flow to Flutter. Users continue to interact with the native app, but when they navigate to the money transfer section, it seamlessly switches to the Flutter-based component. This approach enables small, manageable migrations while maintaining the ability to release updates to both the native and Flutter parts of the app.
The pros of the incremental migration
The incremental migration approach offers several key benefits, making it a flexible and safer option for transitioning to Flutter:
• Lower risk: By migrating the app feature by feature, you reduce the risk associated with large-scale rewrites. You can test, validate, and release new Flutter-based features while the rest of the app remains stable in its native form.
• Continuous delivery: Since the native app remains functional, new features and bug fixes can continue to be delivered to users while the migration is ongoing. This is essential for products with frequent updates.
• Gradual skill transition: Teams can gradually become familiar with Flutter’s architecture, allowing developers to ramp up their expertise over time instead of learning everything all at once.
The cons of the incremental migration
While incremental migration has its advantages, it also comes with some challenges:
• Plumbing work: The initial migration requires some groundwork, including setting up authentication, API handling, and error management in Flutter. These are one-time efforts but add complexity early on.
• Hybrid codebase: Managing a mix of native and Flutter components can be challenging, especially if there are dependencies between the two.
• UI inconsistencies: There could be subtle UI/UX differences between native and Flutter components, although Flutter’s extensive design tools can help mitigate this.
When to consider incremental migration
The flow-based migration strategy is most effective when an app's complexity or business needs make a full rewrite impractical. Here are a few examples:
• Your app is constantly evolving, and you can’t afford a feature freeze while transitioning to Flutter.
• The app is large and complex, making a full rewrite in a single cycle unrealistic.
• Your product roadmap involves the addition of new features or the overhaul of existing flows, which can be handled in Flutter.
Why incremental migration is often the better choice when migrating from Native to Flutter
Based on my experience, the incremental approach offers more flexibility and better long-term stability. Most product teams can’t afford to stop releasing updates for months, especially in fast-moving industries like fintech or e-commerce. With incremental migration, you can continue shipping features, maintain user engagement, and manage risks in a more controled environment.
Additionally, incremental migration allows for natural progression into Flutter. Often, when major product changes are required, you can build those in Flutter right away and bypass the need to rebuild them in the future. This not only accelerates migration but also helps your team master Flutter while delivering on immediate business goals.
Conclusion
Migrating from native to Flutter is a complex decision with significant implications for your app’s architecture, delivery timeline, and user experience. While the Big Bang approach may seem appealing for its clean-slate benefits, it carries high risks due to the extended freeze in product development. On the other hand, incremental migration offers a safer, more adaptable strategy that lets you transition to Flutter without sacrificing the ability to release new features and maintain a stable app.
Although both methods have their uses, incremental migration typically provides a smoother path for modernizing apps without disrupting ongoing development.
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