Oleksandr Sarapulov
Verified Expert in Engineering
Android Developer
Kraków, Poland
Toptal member since June 3, 2025
Oleksandr is a certified senior Android engineer with 10+ years of experience developing, shipping, and maintaining large-scale products, focusing on availability, performance, and security. He led the development of corporate features that drove over 200% GMV growth for a global food delivery platform and cut bugs by 75% through robust testing. Oleksandr has contributed to startups and enterprise companies, leveraging expertise in modern technologies, toolkits, and design architecture.
Portfolio
Experience
- Dagger - 7 years
- Model View ViewModel (MVVM) - 7 years
- Retrofit - 7 years
- Kotlin - 5 years
- Clean Architecture - 5 years
- Jetpack Compose - 5 years
- Coroutines - 5 years
- Room - 5 years
Preferred Environment
MacOS, Android Studio, Git, GitHub, Charles, Slack
The most amazing...
...thing I've done is build a corporate food ordering system that drove over 200% GMV growth. I also led key features and testing that cut bugs by 75%.
Work Experience
Senior Android Software Engineer
Global Food Delivery Platform
- Designed and developed new features for and supported existing company application products using modern technologies and development approaches.
- Boosted the company's corporate domain gross merchandise value (GMV) by 80% after designing, developing, and releasing corporate mobile and group order features.
- Increased account activations by 25% and allowance utilization rates by 35% by owning, designing, developing, and releasing features such as my allowance, account linking, company benefits, and allowance reminders.
- Grew new corporate client acquisitions by 15% after owning, designing, developing, and releasing self-signup and gift card features.
- Decreased the bug creation rate within my domain by 75% by increasing unit tests, integration tests, and test automation coverage by 95%, owning and actively contributing to the initiative.
- Reduced the pull request (PR) merge time by 30% by developing Confluence guidelines for effective PR reviews within the domain.
- Contributed to a 220% GMV increase within my domain, over 75% of which is from mobile, which is 2% of the company's GMV.
Senior Android Engineer
International IT Services Vendor
- Built secure Android wallet and verifier applications from scratch that contributed to winning a public-sector tender related to digital credentials.
- Designed and delivered device policy controller (DPC) apps for mobile network clients, enabling entry into a new enterprise security market.
- Collaborated with cross-functional teams in high-compliance environments, meeting strict deadlines and technical standards.
Lead Android Engineer
US-based Fintech Platform
- Reduced app build time by 20% after leading the migration from Java to Kotlin and from XML to Jetpack Compose.
- Cut verification costs by 60% by developing a receiptless cashback feature.
- Increased new user acquisition by 15% by designing and implementing invite-a-friend and ACH payout modules.
Senior Android Engineer
Regional IT Consulting & Outsourcing Provider
- Developed a feature-rich medication reminder app with advanced scheduling, adherence tracking, and notification logic.
- Created a Google services mocking library to support offline and test environments.
- Implemented the full Android stack across projects, including UI, networking, local storage, and test coverage.
Software Engineer
Multinational Electronics & R&D Center
- Developed advanced home screen launcher components and a graphical UI library with custom animated views.
- Built a reusable framework for animation-rich UI components used in internal showcase applications.
- Created automated UI and unit tests to validate the performance and stability of graphical features.
Software Engineer
Boutique Mobile Development Studio
- Designed and developed multithreaded native Android apps with complex UI/UX animations for early-stage startups.
- Built image rendering and caching pipelines to handle large-scale multimedia content efficiently.
- Delivered niche solutions for dating and veterinary applications with offline functionality.
Experience
Corporate Food Ordering Platform with Group Checkout & Benefits
I led the development of several business-critical features, including group checkout flows, account linking, and corporate benefits tracking. These features contributed to over 200% GMV growth in the domain, with 75% of traffic coming from mobile.
To ensure product stability, I initiated and implemented a testing strategy that increased coverage to 95% and reduced bugs by 75%. I also created internal guidelines for PR review processes, decreasing review time by 30%. All features were built using modern Android architecture, with a focus on modularity, reusability, and testability.
Education
Master's Degree in Computer Science
National Technical University of Ukraine "Igor Sikorsky Kyiv Polytechnic Institute" - Kyiv, Ukraine
Bachelor's Degree in Computer Science
National Technical University of Ukraine "Igor Sikorsky Kyiv Polytechnic Institute" - Kyiv, Ukraine
Skills
Libraries/APIs
Retrofit, Android Architecture Components, OpenGL ES
Tools
Git, RxAndroid, Android Studio, Jenkins, Bitbucket, GitHub, Charles, Slack
Languages
Kotlin, Java, GLSL
Frameworks
Dagger, JUnit, Android SDK, Mockito, Dagger 2, Robotium
Paradigms
Model View ViewModel (MVVM), Clean Architecture, Unit Testing
Platforms
Android, Firebase, MacOS
Storage
Realm, SQLite
Other
Computer Science, Jetpack Compose, Room, Coroutines, Custom Views, Multithreading, Design Systems, CI/CD Pipelines, Material Design, Image Processing, Android Development, Android App Development
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