Reinvented fintech app with Kotlin multiplatform development

From siloed to seamless: How we unified fintech mobile development

40%

lower maintenance costs

30%

faster feature releases

50%

higher team efficiency

Challenge

The existing codebase relied on separate native Android and iOS implementations, leading to duplicated effort, inconsistencies, and slower feature development.

Solution

Implementation of Kotlin Multiplatform Mobile (KMM) to share business logic across Android and iOS while maintaining fully native UI experiences.

Tech stack

Kotlin, MongoDB, SQLDelight, Jetpack Compose, Kafka, JUnit, GitHub Actions, Docker.

Client

Our client is a leading mobile financial services provider offering peer-to-peer payments, banking features, and cryptocurrency transactions. To drive innovation and accelerate growth, the company sought a more efficient development approach – one that ensures a flawless user experience while optimizing performance across platforms.

Challenge

Before implementing the new solution, the client encountered several challenges that slowed down development and affected performance. The reliance on separate native Android and iOS implementations led to duplicated effort, inconsistencies, and delays in feature releases.

To overcome these issues, Modsen Kotlin multiplatform developers focused on key objectives:

Unify the development process to reduce duplication and improve efficiency by adopting Kotlin for mobile development.

Maintain a native UI experience while sharing business logic seamlessly.

Enhance developer productivity with a scalable and maintainable codebase.

Ensure a smooth, high-performance user experience across platforms.

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Team

Mobile Engineers

UX Designers

Back-end Engineers

Project Manager

QA Engineers

Team Lead

DevOps Specialist

Development process

Requirements gathering and processing

To streamline development and increase efficiency, we conducted a thorough analysis of the existing system. The team identified key inefficiencies in maintaining separate native Android and iOS codebases, which led to duplication of effort and inconsistencies. By leveraging Kotlin for mobile app development, we aimed to unify the development process while ensuring high performance.

Planning

Embracing an Agile approach, we designed a structured migration strategy to implement Kotlin Multiplatform Mobile (KMM) while maintaining development velocity. Through iterative sprints, specialists listed key business logic components for shared implementation, ensuring measurable improvements at each stage. A phased adoption roadmap was established, enabling incremental KMM integration with continuous testing and feedback loops.

Team assembly

Building the right team was a top priority, and we left nothing to chance. Every engineer was handpicked through a meticulous selection process, ensuring deep expertise in Kotlin multiplatform development. Candidates underwent rigorous technical interviews, with the CTO personally engaging with each finalist to guarantee the highest standards of skill and collaboration. This careful curation resulted in a powerhouse team of Android and backend engineers, fully equipped to drive seamless shared logic implementation.

Design

To deliver a sleek, intuitive user experience, Modsen Design Studio crafted a visually striking and highly functional UI, tailored to enhance usability across platforms. With the UI foundation in place, we embraced a “shared business logic, native UI” strategy, ensuring platform-specific experiences while unifying core functionality with KMM. A shared repository was established, enabling Android and iOS teams to collaborate efficiently, while maintaining full compatibility with the existing Kotlin-based server infrastructure.

Once finalized, the design was seamlessly handed off to the development team, setting the stage for a smooth transition from concept to code.

Product building

To ensure a seamless transition, our engineers introduced KMM behind feature flags, allowing for a controlled, risk-free rollout. This approach enabled us to test and refine shared logic without disrupting the existing user experience.

The migration focused on key backend components, starting with persistence layers and network APIs. By unifying these core functionalities under Kotlin for Android development, we eliminated redundant platform-specific implementations, improving efficiency and maintainability. Additionally, we implemented a streamlined approach to data management and communication between app layers, ensuring seamless integration across platforms.

By gradually expanding KMM’s adoption, we maintained a stable, high-performance app while setting the foundation for a more scalable and efficient development process.

Comprehensive testing

Delivering a seamless, high-performance experience required more than just writing great code, it demanded a rock-solid testing strategy. Modsen QA team implemented automated testing across Android and iOS, ensuring the shared logic functioned flawlessly on both platforms. To push the limits of Kotlin cross platform development, we ran extensive performance tests, making sure efficiency stayed high without introducing lag or excessive resource consumption:

Unit testing

Integration testing

UI testing

Performance testing

Load testing

Regression testing

Security testing

Cross-platform compatibility testing

Integration

Leveraging the expertise of our Kotlin multiplatform developers, we ensured that adopting KMM was effortless. Clear documentation and well-structured guidelines gave developers everything they needed to hit the ground running. Custom internal tooling simplified integration for iOS builds, cutting down setup time and headaches.

Result

Modsen team successfully implemented Kotlin Multiplatform Mobile (KMM) to share business logic across Android and iOS while maintaining fully native UI experiences:

Streamlined development, reducing duplication and improving efficiency.

Maintained a native UI experience, ensuring seamless platform consistency.

Enhanced developer productivity with a scalable and maintainable codebase.

Delivered a smooth, high-performance user experience across Android and iOS.

40%

reduction in maintenance costs

30%

faster feature releases

50%

increase in team efficiency

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