SoFi

SoFi is a leading financial technology company that offers an all-in-one super app for its nearly 15 million members. From banking and investing to lending products and financial insights, the digital experience is critical to SoFi’s members, who rely on the app for time-sensitive tasks like placing trades or making payments on time. Because reliability and security are paramount, SoFi needed an efficient mobile development platform to deliver a high-quality experience without doubling their engineering efforts.

Previously, SoFi maintained separate native iOS and Android applications. This native-only approach meant they had to build everything twice, which led to inconsistencies in the user interface and doubled the time needed for implementation. From managing separate A/B testing pipelines to coordinating distinct user research cycles, the development process overhead became unsustainable.

Why Flutter?

SoFi's early explorations showed that Flutter offers both a better developer experience and a superior user experience. As they evaluated the technology, the team appreciated Flutter's flexibility, which enabled developers to work in fine detail on custom animations and motion effects. With a promising initial proof of concept, SoFi gradually increased its investment in Flutter to unify its mobile development under a single, high-performing codebase.

Their solution: Building with Flutter

To ensure stability and security during the migration, the team chose an in-place rewrite strategy (often referred to as Add-to-app). They integrated a standalone Flutter module into their existing native context, letting them rewrite features one by one. As features were built in Flutter, the team deployed them behind feature flags, allowing them to gradually shut down the old native implementations.

To maximize velocity, SoFi leveraged a package-based architecture with example apps. This setup made it possible for individual teams to develop and test features locally inside independent packages, significantly reducing developer iteration times. It also optimized their CI pipeline by letting them target builds, run tests, and execute screenshot tests only on the packages that had changed. With developers freed from constantly debugging crashes, SoFi's mobile core team transitioned to building advanced tools and internal systems that make the entire engineering organization more effective.

Key results and business impact

By adopting Flutter, SoFi transformed its mobile development workflow and achieved significant business and technical wins:

• Achieved a 60% reduction in lines of code on a feature-per-feature, apples-to-apples comparison.
• Deleted over one million lines of code overall during the migration.
• Slashed the time required for code reviews, local builds, and iteration cycles.