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Marcin Szeptun

@marcinszeptun

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Senior Android developer focused on performant, secure, user-centered mobile apps.

Poland

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What I'm looking for

I’m looking for a senior mobile role where I can own Android features, mentor engineers, improve architecture, and deliver secure, high‑quality user experiences in a collaborative, growth‑focused team.

I am a Senior Android developer with extensive experience building and owning features for high‑scale consumer and fintech mobile applications. I have led Android projects, introduced Jetpack Compose, and driven architecture improvements while mentoring teammates to raise code quality.

At companies from startups to large teams I delivered secure wallet and payment solutions, video upload features using AWS, onboarding optimizations, and migrated apps from Java/MVP to Kotlin and modern architectures. I prioritize testing, performance, and maintainable architecture including MVVM/MVI, Clean Architecture, and DI with Dagger/Hilt/Koin.

I bring strong cross‑functional collaboration with backend, iOS, design and product teams, a growth mindset, and a focus on measurable user outcomes such as conversion, stability, and efficiency.

Experience

Work history, roles, and key accomplishments

Current

Senior Android Developer

Current

Housecall Pro

Sep 2024 - Present (1 year 9 months)

Develop and own finance-related features in the Housecall Pro Android app, manage releases and user feedback, and implemented a partial large video upload using an AWS solution to improve media handling.

Kotlin Android Development Coroutines Jetpack Compose AWS MVVM Retrofit

Senior Android Developer

Vero

Aug 2022 - Jul 2024 (1 year 11 months)

Owned multiple Android features for a social app used by millions, introduced Jetpack Compose and best practices, and mentored developers to improve code quality and performance of image loading.

Kotlin Jetpack Compose Android Development Coroutines MVVM Mentoring

Android Developer

BlockFi

May 2021 - Aug 2022 (1 year 3 months)

Worked on the BlockFi Wallet onboarding feature to increase registration conversion, refactored the Android codebase toward Clean Architecture, and created a Compose-based design system.

Kotlin Android Development Clean Design Jetpack Compose Coroutines Onboarding Refactoring Testing

Android Developer, Project Leader

PayEye

Jun 2020 - May 2021 (11 months)

Led Android development for PayEye Wallet, designed secure app architecture, implemented secure storage and anti-tamper measures, and built custom views and notification integration with POS terminals.

Kotlin Storage Custom Views POS Integration MVVM

Android Developer

Ryanair

Jul 2018 - Jul 2020 (2 years)

Migrated Ryanair Discovery Android app from Java/MVP to Kotlin and MVVM/MVI, implemented unit and UI tests, enabled Instant App support, and worked on analytics and A/B testing to optimize user experience.