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I build production-grade Android apps using Kotlin and Jetpack Compose — the modern Android stack that most developers are still catching up to. In my day job, I was promoted from Trainee to Junior Software Engineer in just 3 months for shipping features ahead of schedule. On Upwork, I've delivered apps for clients across different industries, earning $1,200+ with a strong track record of on-time delivery. What I bring to your project: ✔ Native Android development with Kotlin & Jetpack Compose (no outdated XML) ✔ MVVM + Clean Architecture for maintainable, scalable codebases ✔ Firebase (Auth, Firestore, Realtime DB, Cloud Messaging) ✔ REST API integration with Retrofit + OkHttp + Coroutines ✔ Offline-first apps with RoomDB & Kotlin Flows ✔ Cross-platform apps targeting both Android & iOS using Kotlin Multiplatform (KMM) I take full ownership of my work — from understanding requirements to writing code, testing, and deploying to the Play Store. I communicate clearly and proactively, so you're never left wondering about the status of your project. If you need a reliable Android developer who writes clean, modern code and actually meets deadlines — let's talk.

🏆 TOP RATED | Top 10% Freelancer on Upwork I build high-quality, production-ready mobile apps for startups, entrepreneurs, and established businesses. From idea → design → development → backend → payments → App Store & Google Play submission — I handle the full mobile lifecycle. I specialize in mobile app development, including custom iOS apps, Android apps, and Flutter cross-platform apps. If you’re looking to build or scale a full mobile product, I can take it from concept to a store-ready release with clean architecture and fast iteration. With 100% Job Success, Top Rated status, and experience delivering complete apps from scratch, I focus on reliability, clear communication, and real business results. What I specialize in • 📱 Flutter cross-platform apps (clean UI, scalable architecture, localization, animations) • 🤖 Android Native (Kotlin · Jetpack Compose) • 🍎 iOS Native (Swift · SwiftUI) • ⚙️ Backend integrations: Node.js, FastAPI, Postgres, AWS RDS, Firebase • 💳 Payments & monetization: Stripe (Subscriptions, Connect platforms, one-time payments), in-app purchases • 🔐 Authentication (Google, Apple, email/password, OTP) • 📦 Push notifications, deep links, scheduling, background tasks • 🚀 App publishing (TestFlight, Google Play, certificates, provisioning) What clients appreciate • Fast and clear communication • End-to-end delivery (you don’t need multiple developers) • Pixel-perfect UI implementation • Strong debugging skills — I fix what others cannot • Reliable, long-term collaboration • Clean, maintainable code Availability • Available daily • Time zone: EST (US Eastern Time) • Quick response and consistent updates 💬 Ready to get started? Let’s talk.

Senior Android Engineer with 9+ years of experience building, scaling, and maintaining high-quality Android applications used by thousands to millions of users worldwide. I help startups, businesses, and product teams develop Android apps that are reliable, scalable, and built for long-term growth. Whether you need a new application, help modernizing an existing codebase, performance improvements, AI-powered features, or urgent production fixes, I can jump in and deliver results quickly. Over the years, I have worked on large-scale production applications across media streaming, audio technology, advertising monetization, analytics, subscriptions, and real-time user experiences. My experience spans the entire Android development lifecycle—from architecture and implementation to CI/CD automation, release management, and ongoing maintenance. What I Can Help You With ✅ Native Android Development (Kotlin & Java) ✅ Jetpack Compose & Modern Android Architecture ✅ MVVM, Clean Architecture & Modularization ✅ Bug Fixing, Crash Resolution & Technical Debt Reduction ✅ Legacy App Modernization ✅ REST API & WebSocket Integration ✅ Media Streaming Apps (ExoPlayer, Audio, Video & DRM) ✅ AI-Powered Features & LLM Integrations ✅ Firebase & Real-Time Data Synchronization ✅ Room Database & Offline-First Applications ✅ Google Play Billing & Subscription Systems ✅ Push Notifications (FCM) ✅ Ad Monetization (AdMob, Appodeal, Meta, Instreamatic & More) ✅ CI/CD Automation (GitLab CI, GitHub Actions & Fastlane) ✅ Google Play Store Deployment & Release Management Why Clients Work With Me ✔ 9+ years of professional Android development experience ✔ Strong experience working on production applications with large user bases ✔ Fast onboarding into existing codebases ✔ Clean, maintainable, and scalable code ✔ Clear communication and proactive problem-solving ✔ Reliable delivery and long-term support I don't just build features—I help businesses create better mobile products by improving stability, performance, user experience, and maintainability. If you're looking for a senior Android engineer who can contribute immediately and take ownership of technical challenges, I'd be happy to discuss your project.

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

I help businesses build reliable, production-ready mobile applications using Flutter. Whether it's developing a new product from scratch or improving an existing codebase, I focus on delivering maintainable, scalable solutions with a great user experience. I have experience building applications for Android and iOS, integrating REST APIs, Firebase services, authentication, push notifications, payments, maps, and offline functionality. I also develop backend services using Node.js and Firebase to support mobile applications. I value clear communication, realistic timelines, and writing code that is easy to maintain long after the project is complete. I provide regular progress updates and work closely with clients to ensure the final product meets their business goals. Core Technologies Flutter & Dart Firebase (Authentication, Firestore, Cloud Messaging, Storage) Node.js & Express Kotlin (Android) REST APIs PostgreSQL & Supabase Git & CI/CD

Need someone who can build, stabilize and scale your Android product? You found him 🤝 📊 12+ years in mobile delivery 📊 20+ Android-focused projects 📊 10+ years with regulated and business-critical products 📊 30+ production Android release cycles 📊 5+ years in Kotlin-first development 📊 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 🔹 Native Android engineering with modern architecture and Software Design 🔹 Kotlin-first development for maintainability 🔹 Legacy modernization Java to Kotlin 🔹 Secure integrations, performance tuning, release stability 🔹 Product delivery for Healthcare, FinTech, consumer platforms and Mobile App Development I’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 ✅ Android development using Kotlin and Java ✅ Architecture design with MVVM, Clean Architecture, modularization ✅ Backend communication, authentication and payment integrations ✅ Performance optimization, debugging, maintenance and release support ✅ 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 🔸 Healthcare mobile applications with compliance-aware architecture 🔸 Secure data handling and app stability improvements 🔸 Secure apps with payment integration and transaction-safe flows 🔸 Backend integrations with PHP, Python, JavaScript, and REST APIs 🔸 Collaboration with iOS, backend, QA, full stack developer 🔸 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 🔸 Android kotlin with Jetpack, Compose, Android SDK, AOSP 🔸 Java, Firebase, secure cloud services, CI/CD 🔸 REST APIs, secure auth, payment gateways, mobile app development api 🔸 Node.js, JavaScript, C#, SQL backend alignment 🔸 Git, Android Studio, release workflows, crash analysis 🔸 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 🔹 Coordination with a rest api developer 🔹 Alignment with web application development 🔹 Communication with a web developer or front end developer 🔹 Familiarity with database builder, django, and python automation Support I Can Provide ✔️ Build a mobile app from scratch ✔️ Join an existing product as an app developer android ✔️ Refactor legacy code modernize architecture ✔️ 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. 📬 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.