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Denis User

@castasat

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Android engineer and founder specializing in Kotlin mobile apps, technical leadership, and rapid MVP delivery.

Montenegro

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What I'm looking for

I seek hands-on mobile engineering or technical leadership roles where I can build scalable Kotlin apps, mentor teams, and drive rapid MVP delivery with strong engineering practices.

I am an Android engineer and founder with eight years of experience building Kotlin-based mobile applications and leading boutique B2B development services.

I have driven product impact—implementing features that increased user engagement by ~15% and managing transitions for 100,000+ users—while establishing agency processes that improved on-time delivery to 95%.

I architect and implement modern Android solutions using Clean Architecture, Jetpack Compose, multi-module design and robust CI/CD practices, and I routinely refactor legacy codebases to reduce bug-fix cycles and increase test coverage.

I hire and mentor cross-functional teams, lead client negotiations and project delivery, and am eager to bring hands-on technical leadership and collaborative problem-solving to teams building industry-leading mobile products.

Experience

Work history, roles, and key accomplishments

Current

Founder / Lead Mobile

Current

Lorem Ipsum DOO

Oct 2025 - Present (3 months)

Founded and scaled a boutique IT agency delivering B2B mobile and hybrid apps; drove client acquisition, led cross-functional teams (3–8), and improved on-time delivery to 95% while accelerating initial project delivery by ~30%.

Kotlin Jetpack Compose Koin Retrofit CI CD

Senior Android Engineer

Beeline Taraz

Nov 2022 - Oct 2025 (2 years 11 months)

Led development of key streaming features (offline listening, infinite playback) increasing user engagement by ~15% and managed transition to a freemium model for 100,000+ users while improving feature adoption via A/B testing.

Kotlin Jetpack Compose Firebase Remote Config Coroutines Retrofit Yandex AppMetrica A B Testing

Senior Android Engineer

Sberbank

Sep 2021 - Sep 2022 (1 year)

Engineered advertising and security Android SDKs embedded in 10+ apps producing 5M+ monthly ad impressions; halved SDK release prep time by implementing CI/CD and Maven publishing.

Kotlin Android SDK CI CD Maven Mockito Kaspresso Protocol Buffers

Senior Android Engineer

Evotor

Sep 2019 - Sep 2021 (2 years)

Developed AOSP-based POS applications deployed on 600,000+ devices and led migrations (Android 6→10, RxJava upgrades), reducing malfunction rates by 15% via a GMP-compliant master app and modernization efforts.

Kotlin RxJava Dagger WorkManager Firebase Crashlytics Jenkins ROOM

Android Developer

MoreCargo

Jun 2018 - Sep 2019 (1 year 3 months)

Designed a modular single-activity MVVM architecture to enable an MVP in 5 months and improved UI responsiveness by 15% using reactive RxJava implementations for an Uber-like truck service.

Kotlin Java MVVM RxJava ROOM Unit Testing Git

Junior Android Developer

International OpenYoga Foundation

May 2017 - Jun 2018 (1 year 1 month)

Sole Android developer on a two-person team delivering a secure cryptocurrency wallet (Pranacoin) to Google Play; implemented MVVM, QR-based transactions and local persistence, eliminating critical post-launch bugs.