Piotr – Android, Kotlin, Retrofit

A sports betting application focused on the UK and Irish markets, providing users with access to sports betting services and supporting market-specific betting workflows.

• Developed new native features and secure communication bridges between native Android components and WebView, enabling 400+ interactive events per user session for the William Hill betting app.
• Refactored JavaScript-to-native bridge logic using structured async queues and Kotlin Coroutines, reducing hybrid rendering latency and crash rates in web-dependent flows.
• Leveraged AI coding assistants to accelerate feature delivery, reducing boilerplate generation time and improving code consistency across the team.
• Introduced AI-assisted test generation workflows to scaffold unit and instrumentation tests, increasing code coverage with reduced manual effort.

A mobile platform for a retail chain, combining payment integration with digital ticketing flows to support convenient customer transactions and service access.

• Led payment integration for a new mobile platform for Poland's largest and most popular convenience store chain, by building a coroutine-based Adyen payment module that handled 200K+ transactions with <0.2% failure rate during launch.
• Designed a reusable interface across app modules using a clean multi-module architecture to support future extensions in POS and loyalty services.
• Built and tested public transport ticketing flows with custom validators and state sync logic.
• Ensured full alignment with other teams' API schemas and navigation models.
• Initiated early-stage architecture design to enforce code consistency across 5 Android developers, establishing common layers for dependency injection, analytics, and navigation.

A national digital identity application for Poland, providing citizens with secure access to digital identification and public services.

• Acted as sub-team lead for 4 engineers while re-architecting Poland's national digital ID app using Clean Architecture, MVI, and Jetpack Compose, driving its rating to 4.8 on Google Play.
• Led the overhaul of the digital document system by building a generic rendering engine, reducing code duplication and enabling integration of multiple document types.
• Designed a phased migration strategy for legacy Java modules using modern Kotlin wrappers, ensuring parallel feature delivery without disrupting stability.
• Coordinated sprint execution, architecture decisions, and delivery of core modules including appointment booking, login, and document syncing.
• Maintained a strong security focus in backend communication and in storing encrypted sensitive data on the device.

A consultant application used by sales representatives to manage customer relationships and product catalogs, supporting efficient sales activities and customer interactions.

• Led end-to-end Android development for a consultant app, used by 50,000+ sales representatives to manage customers and catalogs: worked closely with iOS, backend, and QA counterparts to ensure stable cross-platform parity.
• Worked closely with iOS, backend, and QA counterparts to ensure stable cross-platform parity.
• Refactored server-driven UI logic by introducing a modular rendering layer, improving maintainability, and decoupling visual behavior from release cycles via backend-defined configurations.
• Applied reactive programming patterns with Kotlin Flow to enhance UI state consistency and minimize event-handling bugs.
• Maintained a clean and testable codebase with strong abstraction layers and automated UI testing, accelerating development velocity for future releases.

A mobile banking application supporting secure money transfers, currency exchange, and access to multiple accounts, providing users with convenient tools for managing their finances.

• Co-developed a mobile banking app for supporting secure transfers, currency exchange, and multi-account access: handled 200,000+ users.
• Designed a modular and scalable architecture using Clean Architecture and Dagger2.
• Integrated encrypted local storage with Android Keystore to meet PSD2 compliance.
• Led code reviews, ensured high test coverage, and supported architecture decisions that improved long-term maintainability across banking modules.
• Maintained a strong focus on app security.