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Vadim P.

Barcelona, Spain

$30/hr
5.0
22 jobs

Need someone who can build, stabilize and scale your Android product? You found him ๐Ÿค ๐Ÿ“Š 12+ years in mobile delivery ๐Ÿ“Š 20+ Android-focused projects ๐Ÿ“Š 10+ years with regulated and business-critical products ๐Ÿ“Š 30+ production Android release cycles ๐Ÿ“Š 5+ years in Kotlin-first development ๐Ÿ“Š 4 product areas: compliance-ready apps, secure payments, backend-heavy systems and Software Development I help companies build secure, maintainable apps Healthcare, FinTech, consumer products. Core Expertise ๐Ÿ”น Native Android engineering with modern architecture and Software Design ๐Ÿ”น Kotlin-first development for maintainability ๐Ÿ”น Legacy modernization Java to Kotlin ๐Ÿ”น Secure integrations, performance tuning, release stability ๐Ÿ”น Product delivery for Healthcare, FinTech, consumer platforms and Mobile App Development Iโ€™m an android developer focused on reliability and clean architecture. As a kotlin developer, I build scalable solutions with android kotlin best practices, Jetpack tooling and AOSP awareness. Clients come to me for android developer kotlin expertise when they need stability, lower technical debt and growth. I work as an android app developer on products that need more than interface implementation. I support teams with android app development for secure solutions where every android app stays maintainable after launch. My background: improving an android application used by thousands of users, integrating backend systems, payment flows, and healthcare-grade data handling. That is why companies hire me as an android mobile developer ( android mobile app developer ) when they need delivery. What I Do Best as ai mobile app developer โœ… Android development using Kotlin and Java โœ… Architecture design with MVVM, Clean Architecture, modularization โœ… Backend communication, authentication and payment integrations โœ… Performance optimization, debugging, maintenance and release support โœ… Application Improvement for live mobile products My strongest specialization is android developer kotlin work. I join teams that need android developer kotlin java skills to modernize legacy code, migrate modules, and improve release quality without a full rewrite. That benefits from practical experience as a java developer from thinking like an android kotlin developer who can handle new features and stabilization. Relevant Experience Highlights as a full stack mobile app developer ๐Ÿ”ธ Healthcare mobile applications with compliance-aware architecture ๐Ÿ”ธ Secure data handling and app stability improvements ๐Ÿ”ธ Secure apps with payment integration and transaction-safe flows ๐Ÿ”ธ Backend integrations with PHP, Python, JavaScript, and REST APIs ๐Ÿ”ธ Collaboration with iOS, backend, QA, full stack developer ๐Ÿ”ธ Ability to scale from one engineer to a delivery team I also have experience with android ble, android bluetooth features for pairing flows, reliable data exchange. Whether I contribute to an android mobile app or support an existing codebase as a mobile developer, I focus on release readiness, ai mobile app development. Tech Stack ๐Ÿ”ธ Android kotlin with Jetpack, Compose, Android SDK, AOSP ๐Ÿ”ธ Java, Firebase, secure cloud services, CI/CD ๐Ÿ”ธ REST APIs, secure auth, payment gateways, mobile app development api ๐Ÿ”ธ Node.js, JavaScript, C#, SQL backend alignment ๐Ÿ”ธ Git, Android Studio, release workflows, crash analysis ๐Ÿ”ธ MVVM, Clean Architecture, modular apps, scalability-first mindset My work is rooted in native Android, but I also understand broader product ecosystems. I collaborate effectively as an ios developer ( ios app developer ) when cross-platform alignment matters, including iOS Development discussions with teams using Swift. I have worked alongside teams using react native and reviewed delivery implications where flutter developer was involved, though I do not present those as my core specialization. That exposure helps me operate as an android developer and product-minded mobile app developer within cross-functional teams. Team & Product Collaboration ๐Ÿ”น Coordination with a rest api developer ๐Ÿ”น Alignment with web application development ๐Ÿ”น Communication with a web developer or front end developer ๐Ÿ”น Familiarity with database builder, django, and python automation Support I Can Provide โœ”๏ธ Build a mobile app from scratch โœ”๏ธ Join an existing product as an app developer android โœ”๏ธ Refactor legacy code modernize architecture โœ”๏ธ fix android application bugs and improve release readiness I do not position myself as a wordpress, magento, game developer or unreal engine specialist and I do not use unrelated positioning such as android developer india. Even when someone types android develoer, they usually need a senior specialist who can take ownership. I built mobile applications for autism-related projects with intuitive user experience. ๐Ÿ“ฌ If you need an android developer who can improve an existing product, build a reliable solution from scratch or support growth with kotlin developer depth, send me a message.

  • Kotlin
  • AOSP
  • Mobile App Development
  • Flutter
  • Node.js
  • Android App Development
  • Swift
  • Firebase
  • iOS Development
  • JavaScript
  • Software Design
  • Python
  • ExpressJS
  • SQLite
  • Android SDK
  • iOS SDK
  • Google Play
  • App Store
  • REST API
  • CSS 3
Eugene Z.

Zaporozhe, Ukraine

$30/hr
5.0
20 jobs

๐Ÿ† ๐“๐จ๐ฉ-๐‘๐š๐ญ๐ž๐ ๐๐ฅ๐ฎ๐ฌ ๐Œ๐จ๐›๐ข๐ฅ๐ž ๐€๐ฉ๐ฉ ๐ƒ๐ž๐ฏ๐ž๐ฅ๐จ๐ฉ๐ž๐ซ (๐“๐จ๐ฉ ๐Ÿ๐ŸŽ%) ๐Ÿ† | ๐Ÿ๐ŸŽ๐ŸŽ% ๐‰๐จ๐› ๐’๐ฎ๐œ๐œ๐ž๐ฌ๐ฌ ๐’๐œ๐จ๐ซ๐ž | ๐ข๐Ž๐’ & ๐€๐ง๐๐ซ๐จ๐ข๐ ๐€๐ฉ๐ฉ ๐ƒ๐ž๐ฏ๐ž๐ฅ๐จ๐ฉ๐ž๐ซ | ๐’๐ฐ๐ข๐Ÿ๐ญ | iOS App Developer Swift | ๐Š๐จ๐ญ๐ฅ๐ข๐ง | Android App Developer Kotlin | ๐‘๐ž๐š๐œ๐ญ ๐๐š๐ญ๐ข๐ฏ๐ž | ๐…๐ฅ๐ฎ๐ญ๐ญ๐ž๐ซ | ๐Ÿ–+ ๐˜๐ž๐š๐ซ๐ฌ Iโ€™m a Mobile App Developer focused on building scalable, secure, and production-ready mobile products for iOS and Android ecosystems. My work combines mobile app development, mobile app design, clean architecture, API integrations, Firebase workflows, authentication, analytics, payments, push notifications, and long-term product support. I focus not only on features, but also on performance, stability, maintainability, and business growth. As an iOS App Developer Swift specialist, I deliver native Apple ecosystem solutions through Swift, ios development, ios mobile app development, ios swift engineering, App Store readiness, watchos, apple watch, watchkit, and smart watch integrations. My iOS experience covers MVPs, product recovery, scalable production systems, enterprise apps, and secure ios applications. As an iOS App Developer Swift expert, I focus on polished UI, reliable architecture, optimized performance, and maintainable code. As an Android App Developer Kotlin specialist, I build native Android apps using Kotlin, android app development, android development, modular architecture, Firebase, APIs, payments, analytics, authentication, and production-ready release workflows. My Android App Developer Kotlin work includes scalable android app, android app developer, android application, and complex mobile ecosystems designed for long-term growth. As an Android App Developer Kotlin expert, I focus on clean architecture, stable performance, security, and maintainable Android products. I work as an iOS App Developer Swift and Android App Developer Kotlin for businesses that need reliable native mobile development, strong technical decisions, and product-focused delivery. This native expertise helps create secure ios and android solutions for fintech, e-commerce, booking platforms, fitness, health, taxi, transportation, delivery, dating apps, social media app, live streaming app, video streaming systems, AI-based mobile systems, SaaS, business apps, wearables, and IoT. When product goals require faster launch or flexible delivery, I also support react native mobile, react native developer, react native expert, react native app, react developer, react js, react redux, react node, react native firebase, cross platform mobile development, cross platform mobile, hybrid app, hybrid app developer, flutter, flutter developer, flutter dart, flutter firebase, and flutter app workflows. โญ๏ธโญ๏ธโญ๏ธโญ๏ธโญ๏ธ โ€œReliable mobile app developer delivering stable releases. From MVP recovery to scalable production systems.โ€ ๐ŸŽฏ What I bring: โœ”๏ธ 8+ years as a mobile app developer across full mobile app development lifecycles. โœ”๏ธ Strong iOS App Developer Swift background for native ios app, ios developer, senior ios developer, ios app developer, and scalable swift ios development. โœ”๏ธ Strong Android App Developer Kotlin background for native android developer work, kotlin developer workflows, android app development, and enterprise Android delivery. โœ”๏ธ Experience with API integrations, Firebase, authentication, analytics, payments, push notifications, backend coordination, wordpress, shopify, and mobile app marketing. โœ”๏ธ Product collaboration with mobile app designer, mobile app developers, product teams, and business stakeholders. ๐Ÿ“ฑ Mobile Applications I Develop: โ€ข Taxi & Transportation Apps โ€ข Booking platforms โ€ข Fitness & Health Apps โ€ข AI-based mobile systems โ€ข Security-focused ios and android solutions โ€ข Fintech & Payments Apps โ€ข E-commerce apps connected with wordpress and shopify โ€ข Business & SaaS applications โ€ข Social media app, live streaming app, and video streaming platforms โ€ข Wearables & IoT systems with watchos, apple watch, watchkit, and smart watch โ€ข Delivery and Dating Apps ๐Ÿš€ Technologies & Skills I architect scalable ecosystems combining native and cross-platform engineering. iOS App Developer Swift products are powered by Swift, ios developer swift workflows, ios development, ios swift delivery, App Store readiness, and iOS App Developer Swift expertise. Android App Developer Kotlin products are powered by Kotlin, android application architecture, Firebase, API connectivity, and Android App Developer Kotlin expertise. I also deliver react native, flutter, hybrid app, and cross platform mobile ecosystems. As an iOS App Developer Swift professional, I help teams build polished iOS applications that are easy to scale. With both iOS App Developer Swift and Android App Developer Kotlin expertise, I support full-cycle mobile app development. iOS App Developer Swift and Android App Developer Kotlin delivery stays production-focused. ๐Ÿ“ฉ Ping me. Letโ€™s build something great.

  • Kotlin
  • iOS Development
  • Android App Development
  • Mobile App Development
  • Android
  • Node.js
  • Swift
  • React Native
  • Flutter
  • Mobile App
  • App Development
  • Mobile App Design
  • Mobile App Redesign
  • Web Development
  • Smartphone
  • Software Development
  • React
  • JavaScript
  • Mobile App Testing
  • Product Development
Dmitriy C.

Dnipro, Ukraine

$40/hr
5.0
34 jobs

As a Senior Native Android Developer & Mobile Developer with 10 years in the trenches, I help startups, SMBs, and founders fix "vibe-coded" apps, ship MVPs in weeks, build high-performance apps from 0 to launch, and integrate on-device AI / LLMs to save cloud costs. โœ… 10 years of native Android & Kotlin experience (4y Java + 6y Kotlin) โœ…๏ธ 30+ projects successfully delivered โœ…๏ธ 100k+ MAU app development experience โœ…๏ธ 4.5+ average rating across launched Google Play apps โœ… Under 0.1% crash & ANR rate across all launched apps โœ…๏ธ 5-star feedback from past clients โœ…๏ธ $100k+ earned on Upwork with Top-Rated status โœ…๏ธ 100% JSS โœ…๏ธ Hands-on experience with Kotlin Multiplatform ( KMP , CMP ) In 2026 I specialize in: - on-device AI integration using MediaPipe / LiteRT / Google ML Kit / TensorFlow ( Object detection , Face detection , Pose detection , Text summarizing, OCR , TTS, STT ); - video / media editing apps ( FFMpeg , AndroidX Media3 , MediaCodec ); - build, improve and maintain media , social , edtech, utility, productivity tools); - performance optimization , bug fixing , firebase crash resolution and ANRs ๐ŸŒŸ๐ŸŒŸ๐ŸŒŸ๐ŸŒŸ๐ŸŒŸ Recent feedback : "I was particularly impressed by his strong attention to detail - nothing was overlooked, and the quality of the work consistently met high standards. He showed real commitment to the project, staying engaged and proactive throughout the development process. His regularity and consistency in delivering work made collaboration smooth and reliable." - Neil ๐Ÿš€ Also I've been building my own Android apps so that gives me a deep understanding of not only a technical part but also ASO and monetization strategy. โœ…๏ธ Recent large-scale projects: --- PDF Maker & Reader (130k+ installs , ๐ŸŒŸ4.6 on Google Play) Role: Android Developer / Android App Developer / Kotlin Developer I recently built this high-performance Android app from scratch based on Figma mockup using Kotlin. It allows users to quickly convert images to PDF and edit existing PDFs using a fast, local-first architecture. The app has achieved 130k+ downloads and 8k monthly active users on Google Play, with the crash rate lower than 0.1%. --- --- US Medical Education App (COMQUEST for COMLEX & COMAT Prep) Role: Android Developer / Android App Developer / Mobile Developer As part of an international team alongside iOS Developer and Web Developer, I built this Android app from scratch based on Figma designs for US medical students. Continue providing ongoing support for this project, ensuring the mobile app remains a stable and reliable tool for users. --- --- US Automotive Video Suite app Role: Android Developer / Android App Developer / Mobile Developer In collaborating with an iOS Developer and a Full Stack Developer, I built two native Android apps from scratch as a clone of iOS apps (Dealer Video Inventory and Dealer Video Suite) that allows dealers to capture high-quality vehicle inventory videos and photos. These projects helps dealers increase sales through personalized video. --- ๐ŸŒŸ ๐ŸŒŸ๐ŸŒŸ๐ŸŒŸ๐ŸŒŸ "Dmitri is a pleasure to work with. He's Android programming skills are exceptional. He's always professional and easy to work with. He is very methodical in his approach. Which at times has resulted in delivery scheduling slipping a little but I rather have a good product than a hastily put together product. We're continuing to work with Dima for other projects." - Philip Whether you are looking for a Mobile Developer to lead a new project or an Android Developer to optimize an existing Java / Kotlin codebase or optimize performance, my goal is to provide technical clarity and long-term stability. As a team player for cross-platform projects I have a proven track record of working alongside iOS developers to ensure smooth releases. I also have specific experience collaborating with Flutter Developers and Full Stack Developers to bridge the gap between cross-platform Flutter / React Native code and the system features specifically by developing custom Java / Kotlin modules to handle native Android OS functionality that standard Flutter plugins can't reach. --- ๐Ÿš€ My core stack: ๐Ÿ”ธ๏ธLanguages: Java , Kotlin ๐Ÿ”ธ๏ธUI: XML , Jetpack Compose ๐Ÿ”ธ๏ธArchitecture: MVVM , MVI , Clean Architecture ๐Ÿ”ธ๏ธNative: Android SDK , Android Studio ๐Ÿ”ธ๏ธMultiplatform: Kotlin Multiplatform ( KMM / KMP ) / Compose Multiplatform ( CMP ) ๐Ÿ”ธ๏ธKey features: Camera , Photo & Video capture and edit using FFMpeg , OpenGL , OpenCV ; GPS , Location , Chat , Background syncronization , WorkManager and foreground services, ofline-first approach, on-device AI / LLM , VPN / WireGuard , ExoPlayer / Media3 ๐Ÿ”ธ๏ธOn-device AI integration : Video analysis , Image recognition , Object detection , Face detection , Pose Detection , Camera stream analysis , Text-to-Speech , Speech-to-Text ( MediaPipe / Google AI Edge , TensorFlow / TFLite , Google ML kit ). ๐Ÿ”ธ๏ธCloud AI integration : OpenAI , Gemini API

  • Kotlin
  • Android App Development
  • JavaScript
  • Android
  • Java
  • Mobile App Development
  • Android Studio
  • Smartphone
  • Firebase
  • React Native
  • Android SDK
  • iOS Development
  • Git
  • Flutter
  • AOSP
  • Software Testing
  • Python
  • SQL
  • Swift
  • CSS
Vladimir B.

Kirovograd, Ukraine

$40/hr
5.0
3 jobs

โœ… Available for FULL TIME Work โœ… Expert in Mobile & ๐€๐ˆ-๐๐จ๐ฐ๐ž๐ซ๐ž๐ ๐€๐ฉ๐ฉ Development โœ… ๐€๐ˆ-๐๐จ๐ฐ๐ž๐ซ๐ž๐ ๐Œ๐จ๐›๐ข๐ฅ๐ž ๐๐ซ๐จ๐๐ฎ๐œ๐ญ๐ฌ, ๐€๐ˆ ๐€๐ ๐ž๐ง๐ญ๐ฌ & ๐‹๐‹๐Œ ๐ˆ๐ง๐ญ๐ž๐ ๐ซ๐š๐ญ๐ข๐จ๐ง๐ฌ โœ… Android โ€ข iOS โ€ข Flutter โ€ข Kotlin ๐Ÿ‘€ Click Hire or Invite Senior Android Developer & Mobile Architect ๐Ÿ‘‰ ๐–๐‡๐€๐“ ๐˜๐Ž๐” ๐†๐„๐“ โœ”๏ธ Senior Android Developer - 15+ years of experience, 2,000+ jobs completed on Upwork, 100% project success, scalable architecture deployment, and extreme client impact. โœ”๏ธ Android Developer Kotlin Specialist - modern modular builds, Jetpack Compose expertise, and production-ready engineering standards. โœ”๏ธ Mobile Developer & App Developer iOS Android Systems - faster release cycles, cross-platform collaboration, and defensive coding setups for startup MVP and enterprise environments. ๐Ÿ‘‰ ๐€๐ˆ-๐๐€๐“๐ˆ๐•๐„ ๐Œ๐Ž๐๐ˆ๐‹๐„ ๐„๐๐†๐ˆ๐๐„๐„๐‘๐ˆ๐๐† ๐„๐—๐๐„๐‘๐“ โœ”๏ธ Strategic ๐€๐ˆ ๐„๐ง๐ ๐ข๐ง๐ž๐ž๐ซ๐ข๐ง๐  & Prototyping - leveraging AI-native workflows, agentic coding systems, and autonomous ๐€๐ˆ ๐๐ž๐ฏ๐ž๐ฅ๐จ๐ฉ๐ฆ๐ž๐ง๐ญ practices to accelerate delivery. โœ”๏ธ Multi-Agent Workflow Orchestration - implementing prompt engineering, spec-driven development, and human-in-the-loop ๐€๐ˆ ๐ž๐ง๐ ๐ข๐ง๐ž๐ž๐ซ๐ข๐ง๐ . โœ”๏ธ ๐€๐ˆ-๐€๐ฌ๐ฌ๐ข๐ฌ๐ญ๐ž๐ Testing & DevOps - utilizing AI-assisted debugging, AI-powered refactoring, screenshot-driven UI iteration, and AI-enhanced CI/CD automation with Docker and Kubernetes. ๐Ÿ‘‰ ๐€๐‚๐‡๐ˆ๐„๐•๐„๐Œ๐„๐๐“๐’ โœ”๏ธ 15+ years, 25,000+ hours, hundreds of applications delivered as a leading Android developer, mobile software engineer, and Android game developer across global markets. โœ”๏ธ 2,000+ contracts successfully executed on Upwork through native Android app development, SDK research, and legacy app modernization projects. โœ”๏ธ 100,000+ active users supported on high-load production environments using RxJava, Dependency Injection, and real-time streaming workflows. โœ”๏ธ 10,000+ active device configurations managed within distributed architectures, utility applications, and BLE sync modules through Android Kotlin refactoring. โœ”๏ธ High-converting customer flows across enterprise mobile solutions, fintech portals, and marketplace applications. โœ”๏ธ Faster background processing and improved efficiency through API integrations, JNI integration structures, and memory-leak profiling. โœ”๏ธ Shorter startup MVP timelines and fewer post-launch defects through Android Java to Kotlin migration and Google Play submission expertise. ๐Ÿ‘‰ ๐–๐‡๐„๐‘๐„ ๐ˆ ๐ƒ๐„๐‹๐ˆ๐•๐„๐‘ โœ”๏ธ As an Android developer Kotlin expert - building reactive systems from scratch using Kotlin, Jetpack Compose, Android Jetpack, and modern architecture components. โœ”๏ธ As an experienced Android Java engineer - handling legacy support, backend API integrations, structural refactoring, and app modernization initiatives. โœ”๏ธ As a cross-functional mobile developer - driving end-to-end product development while collaborating with iOS developers, Flutter developers, and backend engineering teams. โœ”๏ธ As a native application architect - deploying MVVM, MVP, and Clean Architecture optimized for modern Google Play requirements. โœ”๏ธ As a long-term developer - providing ongoing testing and maintenance, feature additions, BLE and sensors integration, deep debugging, and backend support. ๐Ÿ‘‰ ๐ˆ๐๐ƒ๐”๐’๐“๐‘๐˜ ๐ˆ๐Œ๐๐€๐‚๐“ โœ”๏ธ Real-Time Streaming & Utilities - media playback engines, real-time chat synchronization, background processing, and BLE communication. โœ”๏ธ Enterprise & Business Apps - secure offline-first structures, local synchronization, encrypted authentication, and performance optimization. โœ”๏ธ Android Game Development - rendering optimization, frame-rate scaling, interactive animations, and modular gaming logic. ๐Ÿ‘‰ ๐‡๐Ž๐– ๐ˆ ๐๐”๐ˆ๐‹๐ƒ โœ”๏ธ Production-Ready Coding Standards: prioritizing robust Android architectures, responsive UI, API documentation, and clean developer handoff. โœ”๏ธ Agile Development & Scrum Frameworks: technical leadership, rapid feedback loops, and fast prototyping to capture market opportunities. Looking for a reliable Senior Android Developer, Android Developer Kotlin Expert, or an experienced Mobile Developer who can build a native application from scratch, optimize legacy architectures, or orchestrate AI app integrations for long-term collaboration? โ˜Ž๏ธ Let's connect! Send an invite and let's discuss your mobile application goals.

  • Kotlin
  • Android
  • Android NDK
  • Android SDK
  • Android App Development
  • Mobile App Development
  • Android App
  • Android Smartphone
  • Mobile UI Design
  • Smartphone
  • Firebase
  • Google Play
  • Java
  • Native App Development
  • Git
  • App Feature Development
  • Software Debugging
  • iOS Development
  • Software Development
  • Embedded Application
Shahzaib A.

Islamabad, Pakistan

$40/hr
5.0
57 jobs

Are you tired of maintaining two separate codebases for Android and iOS? I help startups and businesses ship both platforms faster with a single, shared Kotlin codebase using Kotlin Multiplatform (KMP) and Compose Multiplatform (CMP). While most developers build for one platform, I specialize in the modern cross-platform stack that reduces your development cost by up to 50% โ€” without sacrificing native performance or user experience. โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€ ๐Ÿ”ง WHAT I BUILD โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€ โœ… Cross-platform apps with shared UI using Compose Multiplatform (CMP) โœ… Shared business logic across Android & iOS with KMP โœ… Native Android apps with Jetpack Compose & Clean Architecture โœ… Migrating existing Android apps to Kotlin Multiplatform โœ… In-App Purchases, subscriptions & RevenueCat / Play Billing integration โœ… Push notifications (FCM / APNs), WebSockets & background processing โœ… REST API & WebSocket integration with Ktor โœ… Local caching with SQLDelight / Room KMP โœ… PDF generation, file handling, document upload & viewers โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€ โš™๏ธ TECH STACK โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€ Cross-Platform : Kotlin Multiplatform (KMP), Compose Multiplatform (CMP) Android : Jetpack Compose, MVVM, Clean Architecture, Coroutines, Flow iOS : SwiftUI interop, Xcode, CocoaPods / SPM integration Networking : Ktor, Retrofit, WebSockets, REST APIs Storage : SQLDelight, Room KMP, DataStore DI : Koin, Hilt CI/CD : GitHub Actions, Fastlane, App Store Connect, Play Console Other : Firebase, OneSignal, RevenueCat, Coil, Kotlin Serialization โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€ ๐Ÿ’ผ REAL-WORLD EXPERIENCE โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€ I've shipped production KMP apps including AI-powered tools that run identically on Android and iOS with shared networking, business logic, background task processing, PDF exports, and subscription flows. I understand both platforms deeply: Android lifecycle, iOS Info.plist entitlements, App Store review guidelines, and Google Play publishing. โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€ โœ… WHY CLIENTS CHOOSE ME โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€โ”€ โ†’ One developer. Both platforms. One codebase. โ†’ Senior-level experience โ€” no hand-holding needed โ†’ Clear communication and on-time delivery โ†’ I write code you can maintain, not spaghetti you'll regret If you want a developer who truly understands Kotlin Multiplatform and Compose Multiplatform not just someone who Googled it โ€” let's talk. Send me a message describing your project and I'll respond within a few hours.

  • Kotlin
  • Android App Development
  • Reactive Programming
  • Java
  • Android SDK
  • JetPack
  • Swift
  • SwiftUI
  • iOS
  • Mobile App Development
  • iOS Development
  • RxSwift
  • Android
  • Hybrid App Development
  • Native App Development
Siarhei L.

Warsaw, Poland

$35/hr
5.0
10 jobs

๐ŸŸข AVAILABLE TODAY, JULY 31. โšก Message me "AUDIT" - get a free 30-min Swift & iOS technical review of your app idea, architecture, or existing Swift codebase. No sales pitch. Just honest Swift engineering feedback. I'm Siarhei - Swift & Kotlin engineer, ex-CTO x 3 funded startups, CEO of Sparkler Soft. We build native iOS (Swift) and Android (Kotlin) products that ship, scale, and raise. ๐Ÿ”ต PROVEN RESULTS โ—ˆ iHairium - AI Hair Diagnostics (Swift, live on App Store) Native Swift + Core ML neural network 100K+ training images, 95-98% accuracy $600K angel round + $5M seed valuation Revenue x10 to x1000 per month in early stages Google & Amazon grants, 1,000+ clinic partners onboarded โ—ˆ Eco-Go - Electric Scooter Sharing Platform Swift (iOS) + Kotlin (Android) + Backend + IoT + Admin Panel AWS IoT Device Management, swappable battery infrastructure Named "Best Startup of the Region" โ—ˆ BLE Wearable App (Swift + Kotlin, App Store + Google Play) HealthKit + Health Connect + RevenueCat subscriptions BLE background sync, AWS IoT Core Shipped on schedule, 5.0 client review โ—ˆ Optics Platform (White-label, Strict NDA) Swift + Kotlin, AI-assisted frame & lens selection via device camera Active in 60+ countries, 1,000+ fitting points worldwide 10+ years on market, award-winning at international exhibitions โ—ˆ Chibbis - Unified Food Delivery Service Swift (iOS) + Kotlin (Android) + Web + Admin Panel + CMS 600+ restaurants, 150+ cities One of the country's leading delivery platforms โ—ˆ CoinForShop - Crypto Marketplace Swift (iOS) + Kotlin (Android) + Web (React) Non-custodial wallets, smart contract payments BTC, ETH, BCH, LTC, XMR, TRX, 100% MVP delivered โ—ˆ Azarium - NFT Real Estate Investment Platform Swift + Kotlin, fractional property ownership via blockchain MAS-regulated, live construction webcam in-app Min investment from $200, expected ROI 30-60% ๐ŸŸ  WHAT WE BUILD WITH SWIFT AND KOTLIN - Native iOS (Swift, SwiftUI, UIKit, Objective-C) - Native Android (Kotlin, Java) - Swift + Kotlin full product: app + backend + admin panel + CMS - HealthTech and AI - Swift Core ML, on-device neural networks, camera diagnostics - TensorFlow Lite, OpenCV, real-time image analysis in Swift - FinTech and Crypto - Swift + Kotlin wallets, KYC/AML, Stripe, smart contracts, NFT - Mobility and IoT - Swift + Kotlin: GPS, BLE, AWS IoT, scooter and bike sharing - Telematics, real-time fleet management - Marketplace and Delivery - Full-stack Swift + Kotlin: app + backend + admin panel + CMS - API Integrations - Stripe, Mapbox, Sumsub, Firebase, HealthKit, any third-party ๐ŸŸก SWIFT AND KOTLIN TECH STACK - Mobile: Swift, SwiftUI, Objective-C, UIKit, Kotlin, Java - Backend: Java Spring Boot, Node.js, NestJS, Golang - Frontend: React, Next.js - AI/ML: TensorFlow Lite, Core ML (Swift), OpenCV - Cloud: AWS, GCP, Azure, Docker, Kubernetes, CI/CD - Data: PostgreSQL, MongoDB, Redis, Elasticsearch - Security: OAuth2, OIDC, JWT, Keycloak, Biometrics, IAP (Swift StoreKit) ๐Ÿ‘‰ Message "AUDIT" right now - 30 minutes to understand if our Swift and Kotlin team is the right fit.

  • Kotlin
  • Swift
  • SwiftUI
  • iOS Development
  • AWS IoT Core
  • HealthKit
  • Android App Development
  • Mobile App Development
  • React
  • Java
  • AI Model Integration
  • Core ML
  • API Integration
  • In-App Purchases
  • Push Notifications
  • Firebase
  • REST API
  • PostgreSQL
  • Payment Gateway Integration
  • Spring Boot

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Kotlin developer hiring guide

Kotlin developers build high-performance Android applications, back-end systems, and cross-platform solutions using the Kotlin programming language. With strong interoperability with Java and support for frameworks like Jetpack Compose and Ktor, Kotlin developers deliver scalable, efficient solutions across industries. 

What does a Kotlin developer do?

A Kotlin developer builds software using Kotlin, a programming language commonly used for Android apps and back-end systems. They work with tools like Android Studio, Jetpack Compose, Ktor, and Firebase to deliver mobile applications, APIs, and server-side development that meet modern business needs. Businesses hire Kotlin developers to modernize their mobile presence, improve code maintainability, and accelerate product development cycles across projects ranging from e-commerce apps to enterprise-scale software development

On a day-to-day basis, Kotlin developers are likely to:

  • Write clean, testable code

  • Implement UI components using Jetpack Compose

  • Build RESTful APIs for seamless data communication between front-end and back-end systems. 

  • Conduct code reviews

  • Write unit and integration tests using frameworks like JUnit and Espresso

  • Collaborate with product managers and designers to translate business requirements into technical solutions

  • Handle app deployment to the Google Play Store

  • Monitor post-launch performance using analytics tools

Kotlin's official backing by Google as the preferred language for Android development has made it a critical skill in the mobile development landscape. Developers proficient in Kotlin can leverage features like null safety, extension functions, and coroutines for asynchronous programming โ€” all of which contribute to building robust, crash-resistant applications that often integrate with existing Java codebases. This makes Kotlin developers especially valuable for businesses that prioritize reliability and user experience in their mobile products.

Whether you need an MVP startup build, a new mobile app, API development, or migration from legacy Java codebases, a skilled Kotlin developer can streamline your workflow and help bring products to market faster.

How to hire a Kotlin developer on Upwork

Hiring a Kotlin developer on Upwork is straightforward. Follow these four steps to find the right match for your project.

Step 1: Craft a targeted job post

The quality of your job post directly influences the caliber of Kotlin developers who apply. Well-defined requirements help experienced candidates self-select and demonstrate relevant expertise in their proposals.

  • A strong mobile app job description is the foundation of attracting qualified Kotlin developers.

  • Be specific about your goals and technical requirements so candidates can quickly assess their fit.

  • Specify the project type, such as mobile app development, back-end API creation, or Java-to-Kotlin migration.

  • List the tech stack required, including Kotlin, Android SDK, Jetpack Compose, Ktor, or Firebase

  • Outline business objectives like scalability requirements, real-time functionality, or e-commerce integration

  • Clarify quality expectations around testing frameworks (JUnit, Espresso) and delivery timelines.

If you want help getting started faster, try Upwork's Job Post Generator, powered by Umaโ„ข, Upwork's Mindful AI. Describe what you need in a few sentences, and Uma will draft a job post tailored for Kotlin developers.

Step 2: Filter and evaluate candidates

A systematic approach to candidate evaluation helps ensure you identify developers with proven track records in Kotlin development. Prioritize real-world project outcomes and technical depth over years of experience alone.

  • Reviewing profiles and portfolios helps you identify developers whose skills and experience align with your project needs.

  • Check for mobile app experience with Kotlin, Android Studio, and Jetpack Compose in their portfolio

  • Assess back-end knowledge, including server-side development, API design, and cloud services like AWS.

  • Review client feedback that highlights code quality, communication, and on-time delivery

  • Look for a high Job Success Score and quality badge that indicates reliable performance on past projects on Upwork.

You can use Upworkโ€™s instant video interviews to screen applicants for a best-fit shortlist, with Uma providing side-by-side candidate comparisons.

Step 3: Interview your top choices

Direct conversations and technical interview questions reveal how candidates approach challenges and communicate complex concepts. This step also helps you assess cultural fit and working style beyond what portfolios can show.

  • Android developer interview questions help you to evaluate both technical depth and collaboration skills.

  • Ask about their development process, including agile methodology, CI/CD pipelines, and version control practices, and explore problem-solving abilities with interview questions about optimizing performance and managing complex codebases.

  • Discuss availability and communication preferences, including time zone overlap and preferred collaboration tools.

Upwork Messages allows you to schedule and conduct live video interviews on the platform, with call transcripts and summaries available after the calls.

Step 4: Agree on scope and begin work

Before starting any work, use Upworkโ€™s contracting step to put a firm agreement in place. Formalizing project parameters before development begins protects both parties and establishes accountability. 

  • Setting clear expectations from the start helps prevent misunderstandings, keeps the project on track, and reduces the risk of scope creep.

  • Define deliverables such as functional mobile applications, APIs, or optimized back-end modules

  • Establish a timeline with milestones for feature releases, code reviews, and testing cycles.

  • Confirm pricing structure, whether project-based or ongoing, aligned with scope and budget.

Upwork is not affiliated with and does not sponsor or endorse any of the tools or services discussed in this article. These tools and services are provided only as potential options, and each reader and company should take the time needed to adequately analyze and determine the tools or services that would best fit their specific needs and situation.


The rates and information provided in this article are based on current data and industry sources available at the time of publication. Freelance rates can vary depending on factors such as experience, location, project scope, and market conditions. Readers are encouraged to conduct their own research to confirm current rates and trends, as this information may change over time.

How much does hiring a Kotlin developer cost?

Kotlin and other mobile app developers on Upwork generally charge $18-$39 per hour. Specific costs of hiring Kotlin developers depends on the developerโ€™s experience level, the project complexity, and the engagement type.

Consider these typical project costs when estimating your budgeting for Kotlin development efforts:

Bug fix and code optimization

$500-$1,500/project

Entry-level
  • Debugging existing Kotlin codebase
  • Performance profiling and optimization
  • Code refactoring for maintainability

Android UI development

$2,000-$5,000/project

Mid-level
  • Custom screen layouts with Jetpack Compose
  • UI component library creation
  • Responsive design implementation

Back-end API development

$3,000-$8,000/project

Mid-level
  • RESTful API design and implementation
  • Database integration with PostgreSQL or SQLite
  • Authentication and security setup

Full Android app build

$8,000-$25,000/project

Expert-level
  • End-to-end mobile app development
  • Third-party API and payment integration
  • App store deployment and testing

Legacy Java-to-Kotlin migration

$5,000-$15,000/project

Expert-level
  • Codebase audit and migration planning
  • Incremental Java-to-Kotlin conversion
  • Post-migration testing and validation

FAQs about Kotlin developers

Frequently asked questions

Is hiring a Kotlin developer worth it?

Yes, hiring a Kotlin developer is worth it if youโ€™re building an Android app, want faster development with less code, need more stability and fewer bugs, or are starting a modern, scalable codebase. Many Kotlin developers are experienced with the entire life cycle of app production and familiar with collaborating with cross-functional teams, making them instrumental in Android development environments. Kotlin's concise syntax also leads to fewer bugs and faster iteration compared to Java, which can significantly improve your time to market.

Which brands use Kotlin?

Many leading tech companies use Kotlin to power their mobile and back-end applications. Google officially supports Kotlin for Android app development, which has accelerated its adoption across startups and enterprise teams. Major brands like Pinterest, Trello, Uber, and Square have integrated Kotlin into their Android codebases for better scalability and maintainability. Companies in fintech, e-commerce, and SaaS also rely on Kotlin because of its strong interoperability with Java and modern development workflows.

Is Kotlin similar to Python?

Kotlin and Python share some similarities in readability, but they serve different purposes. Kotlin is a statically typed language built for app development, back-end systems, and enterprise codebases, while Python is often used for scripting, AI, and data science. Businesses may choose Kotlin for Android app development or server-side workflows, while preferring Python for analytics or machine learning.

Is Kotlin tough to learn?

No, Kotlin isnโ€™t considered difficult for developers with Java or general programming experience. Its syntax is more concise than Java, which can improve productivity and reduce errors. Many Kotlin developers also highlight how tools like Jetpack and Android Studio tutorials lower the learning curve. Kotlin's growing ecosystem of documentation and community resources makes onboarding even smoother for developers transitioning from other languages.