How a Leading Financial Advisor Achieved a Seamless Flutter Migration to Deliver a Better Mobile Experience

We worked with Betterment to pilot Flutter for their application, establish Flutter expertise and best practices, and train their engineering team on the new mobile framework.

The Challenge

Betterment, a leader in digital investing and financial advice, wanted to modernize their mobile app experience and explore Flutter as a potential solution. However, adopting a new technology at scale came with uncertainties and risks:

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• Could new Flutter-code be integrated smoothly with their existing native codebase?
  
  
• How would they migrate their large, legacy native apps to Flutter without rebuilding everything from scratch?
  
  
• How could they ensure that their engineering team—which had little experience with Flutter—could learn it quickly enough to contribute to production code?

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The Solution

To address these challenges, VGV designed a phased, low-risk strategy that would allow Betterment to test Flutter, prove its value, and gradually migrate their app while enabling their engineers. Our work focused on building confidence, creating standards, and setting up long-term success. This included:

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• Piloting Flutter in Their App: Building a non-critical feature (account-creation flow) using Flutter, then integrating it into the existing native code via Flutter’s “add-to-app” functionality. 
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• Designing a Migration Strategy: Creating a plan to migrate pieces of the app gradually, keeping the rest in native, so as to balance risk, maintain stability, and allow incremental progress. 

• Establishing Best Practices & Engineering Standards: Determining standards for writing, organizing, and scaling Flutter code in this hybrid environment.
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• ‍Delivering Training: Upskilling Betterment’s engineers to get them up to speed, so they could build features using Flutter themselves soon after training.

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How We Did It

Our approach combined practical engineering work with hands-on enablement, ensuring both short-term wins and long-term adoption:

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• Flutter Pilot: Built the first feature in Flutter (the account-creation flow), then connected it to the existing native codebase. This proved that “add-to-app” integration works and performs well.
  
  
• Transformation Plan: Rather than rewriting the entire app, we helped plan a phased migration: port portions of the app to Flutter over time, and build all new features in Flutter, while leaving stable parts of native code in place until they are ready to move.
  
  
• Best Practices Implementation: Set up architecture, code organization, tooling, and workflows so that as more of the app is ported, quality and maintainability are preserved.
  
  
• Training & Enablement: Ran formal training sessions (with “Super Declarative!”) for Betterment’s engineering team, including group sessions, hands-on examples, breakout groups. In just one week, engineers went from minimal Flutter knowledge to building features in Flutter that are now part of the production app.

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The Results

775,000+

Betterment Accounts

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20+

Flutter Developers Trained

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$32b

Assets Under Management (as of 3/2023)

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“Even with a talented team, converting two large, legacy codebases into a single codebase using an unfamiliar technology was a challenging proposition. Working with VGV gave us the added confidence we needed to evaluate Flutter, figure out that we love it, and commit to migrating our entire app.” - Sam Moore, VP Architecture, Betterment

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