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Hello! I’m Mikolaj, a full stack web and mobile app developer with 5+ years of experience building production ready mobile apps, SaaS platforms, MVPs, marketplaces, admin dashboards, and AI-powered applications. I specialize in React Native, Expo, Flutter, Swift, Kotlin, Next.js, Node.js, Firebase, Supabase, PostgreSQL, Stripe, RevenueCat, and AWS. I can help you build a new product from scratch, improve an existing MVP, fix bugs, optimize performance, or prepare your app for App Store and Google Play release. What I Can Help You With 📱 Mobile App Development Cross-platform iOS and Android apps using React Native, Expo, and Flutter, with native Swift/Kotlin integrations when needed. I handle architecture, UI implementation, API integration, testing, builds, and store submission. 💻 Web Apps & Admin Panels Modern web applications, dashboards, and SaaS platforms using React, Next.js, TypeScript, and Tailwind CSS. ⚙️ Backend Development Secure and scalable APIs with Node.js, Express, NestJS, Firebase, Supabase, and PostgreSQL. I build authentication, real-time features, subscriptions, chat, notifications, and admin systems. 💳 Payments & Subscriptions Stripe, RevenueCat, in-app purchases, subscription logic, webhook handling, and payment flows for mobile and web apps. ☁️ Deployment & DevOps AWS, Docker, GitHub, CI/CD, app store deployment, production configuration, bug fixing, and performance optimization. Project Types I Work On * MVPs for startups * SaaS platforms * AI-powered mobile and web apps * Marketplaces * Chat and social apps * E-commerce platforms * Booking and on-demand service apps * Internal business tools * Admin dashboards * Subscription-based apps Why Work With Me I take ownership of the full development process, from planning and architecture to launch. I write clean, maintainable code, communicate clearly, and focus on delivering a product that is stable, scalable, and easy to continue building on. I’m especially interested in long-term projects where I can help improve the product, add new features, and support growth after launch. ✨ Let’s build something reliable, modern, and ready for real users. Feel free to reach out and tell me about your project.

With over 8 years of experience, I specialize in developing native Android applications for high-profile clients and businesses. My expertise encompasses the entire app development process, from planning and development to publishing, maintenance, and support, ensuring the delivery of high-quality Android applications. If you're seeking to create functional Android apps with effective design and performance, you've come to the right place. I understand how to satisfy your customers and increase your sales. I take on a limited number of projects at a time, allowing me to provide the necessary focus and time each one deserves. My commitment to quality control ensures that every project receives meticulous attention. Customer satisfaction is my top priority, and I consistently go the extra mile. I empathize with both my clients and their end-users, considering the unique needs, expectations, and preferences of the target audience. Throughout my process, I employ empathic design and techniques to uncover user values and aspirations. Strengths and skills: - Mastery of various architecture patterns, including MVP, MVVM, and MVI. - Proficiency with Firebase services such as push notifications, dynamic linking, analytics, Crashlytics, real-time NoSQL databases, and cloud functions. - Experience with Amazon Web Services, including EC2, API Gateway, S3 Buckets, Lambda functions, and push notifications. - Skilled in Google services like authentication, Google+, voice recognition, image recognition, text processing, and machine learning. - Familiarity with Dropbox storage APIs. - Integration of social media platforms such as Twitter, LinkedIn, and Facebook for authentication, analytics, and crash reporting. - Comprehensive knowledge of various application tools, including background services, system-level communications, file storage, notifications, offline apps, communication apps, wallpaper apps, and system tracking apps. Development tools and professional techniques: • Project Management Tools: Jira, Trello • Version Control Systems: Bitbucket, GitHub, GitLab, etc. • Communication Platforms: Skype, Zoom, Google Meet, Webex, Teams • Android Studio • IntelliJ IDEA • Postman • Charles Proxy I am eager to establish long-term relationships with clients and build a strong, ongoing working partnership. I will ensure that the overall budget is reasonable for you and your team. With lower maintenance costs, you can overcome any obstacles and lead a successful Android product to market.

Looking for a robust, scalable, and high-performance mobile solution? I am a specialized Android Developer with a strong focus on Kotlin Multiplatform (KMP) and modern native development. With a Master's degree in Applied Mathematics and over 5 years of intensive commercial experience, I don't just write code—I solve business problems using technology. My goal is to help you launch products faster and more efficiently, whether it's a complex enterprise solution, a consumer app, or a cross-platform project using KMP. 🚀 What I Bring to Your Project: - Fintech & Security: Proven track record with sensitive financial data, secure APIs, and strict compliance (ATON Investment Co.). - Modern & Legacy Stack: Expert in Kotlin/Jetpack Compose with strong skills in refactoring legacy Java code. - KMP Efficiency: Share business logic between Android/iOS to cut budget and time-to-market. - Complex Integrations: Hardware (NFC, printers), Fiscalization systems, Custom UI, and CI/CD pipelines. 🏆 Key Achievements: - ATON (Fintech): Developed ATON Line investment app for high-net-worth clients. Refactored Java→Kotlin, ensured security compliance, and optimized architecture (MVP→MVI). - Bark (Logistics): Led development of a Kiosk Self-Service App with NFC integration and fiscalization. Worked directly with Chinese technical documentation. - Startups & Enterprise: Built scalable UI Kits, multi-language apps (XmarineIQ), and established CI/CD processes from scratch. 🛠 Tech Stack: Kotlin, Java, Jetpack Compose, KMP, MVVM/MVI, Clean Architecture, Retrofit, Ktor, Room, Koin, Dagger2, GitLab CI/CD, Firebase. I actively use Claude Code (Anthropic's AI coding assistant) as part of my development workflow to accelerate delivery and maintain high code quality. 🤝 Why Work With Me? - Strong Math Background: Ensures logical, optimized, and bug-free algorithms (crucial for finance). - Business-Oriented Mindset: I focus on ROI and product goals, not just closing tickets. - Enterprise Standards: Experienced in code reviews, team collaboration, and delivering stable releases without micromanagement. - AI-Augmented Development: I leverage Claude Code to speed up routine tasks, catch issues early, and keep focus on architecture and business logic — delivering more in less time. I am ready to dive into your project and deliver results that exceed expectations. Let's discuss how I can help bring your app idea to life! 📩 Invite me to your job, and let's get started!

🏆 𝗧𝗢𝗣 𝗥𝗔𝗧𝗘𝗗 𝗣𝗟𝗨𝗦 🏆 ✅ Mobile App Developer 7+ years of experience ✅ SaaS Mobile App Developer 5+ years ✅ 35 mobile app development jobs completed successfully ✅ Android and iOS Mobile Expert ✅ Built 27+ UX-first Mobile App development jobs for 22 companies ✅ On-Time and Cost-Effective Delivery ✅ Future-Proof Solutions Showing a Minimum 41% ROI ✅ 4354 mobile app development hours on Upwork and still counting ✅ 100% Job Success in mobile app development (Client Satisfaction Ratio) ✅ 98% of Clients Recommended working with me ✅ 80% Long-term Repeat Clients ✅ 7+ years of experience in mobile app development, 6 years experience in iOS mobile app development, 7 years experience in Swift and Kotlin, 4 years experience in Flutter, React Native, 2 years experience in KMM, KMP Full stack mobile app developer and mobile app UI UX designer with 7+ years of experience in Mobile App Development, specializing in iOS, Swift, Android, Kotlin, KMM, Kotlin Mutliplatform / KMP, React Native, and Flutter. I have successfully delivered 120+ mobile applications in different roles as mobile app developer, flutter app developer, flutter full stack developer, flutter flow, mobile app design, mobile ui ux designer, swift ios developer, android developer, kotlin developer, react native developer, mobile game developer achieving a 5-star rating on Upwork and helping clients scale their businesses with high-performance solutions. Apart from mobile app development, I specialize in Mobile App Design for both iOS and Android, as well as Web App Design for SaaS platforms. My expertise extends to Interaction Design, User Flow Design, and creating seamless User Experience (UX Design) and User Interface (UI Design). I follow a Design Thinking approach, ensuring every solution is user-centered and problem-solving. My process includes UI/UX Wireframing, Prototyping, and building Style Guides or UI-kits for consistent branding. I perform Design Audits and Design QA to maintain high standards across all projects. 🛠️ Design Tools: My designs come to life through powerful tools like Figma, Zeplin, and InVision for prototyping and collaboration. I leverage Adobe Illustrator, Adobe Photoshop, and Adobe XD for detailed visual design. For complex wireframes and flow mapping, I turn to Axure, Sketch, and Balsamiq. I also use Miro and Abstract for brainstorming and version control, while project communication and management happen in Slack and Jira. Our Expertise at a Glance • Mobile App Development: Android, iOS, & Cross-Platform App Development using Java, Kotlin, Swift, Objective C, Flutter, and more. • Website and Full Stack Development: Crafting seamless back-end experiences with .Net, Python, Java, Javascript, React.js, Angular.js, Node.js, MERN, MongoDB, PHP, etc. • Logo & UI/UX Design: Bringing your ideas to life with Adobe XD, Photoshop, Sketch, Figma, etc. • End-to-End Solutions: From logo design, UI/UX development, workflow setup, testing to deployment in app stores, we've got it all covered. We do not use v0.dev lovable.app CursorAI, Cursor, Windsurf, Trae, GitHub Copilot, Tabnine, Qodo, Devin AI, and AutoDev for speed up coding, we know other methods to do it efficiently. We offer a comprehensive range of development services across mobile, web, and cloud platforms. Our mobile app development expertise includes building Android and iOS applications using technologies such as Flutter, Swift, Objective-C, React Native, and Xamarin, optimized for both smartphones and tablets with a focus on cross-platform compatibility. In website and full stack development, we work with .NET technologies, including full stack .NET development, .NET Core, and Python with Django. Our team is experienced in developing both backend systems and user-friendly, responsive web interfaces, as well as working with various CMS platforms. Our DevOps and DevSecOps capabilities cover cloud infrastructure and automation, leveraging tools like AWS, Azure, Docker, Kubernetes, GitLab CI, Ansible, and Terraform to build secure and scalable deployment environments. We also build cross-platform and web applications using frameworks like Three.js and design tools such as Webflow, creating visually engaging and functional user experiences across devices. Additionally, we are well-versed in integration and automation tools, including WebSockets, data integration, the ABP Framework, Discord API, and Autotask, allowing us to create seamless connectivity and workflow automation between systems. Talent Good Knowledge, Talented, Experienced, Skilled, Strong Experience, Proven Experience, Agency, Team, Company, Specialist, Proven Track Record, Strong Background, Write Clean Code, Deep Expertise, Bring to Life, Cross-platform, Attention to Detail, Long Term. ⚡️ AVAILABLE FOR NEW PROJECTS ⚠️ Press Invite Button on my page and let's talk.

✅ .NET Full Stack Developer 20+ years of experience ✅ Build powerful .Net solutions that drive business growth ✅ C# .Net developer with 15+ years of experience ✅ Developed 50+ applications ✅ Crafted 200+ user-friendly interfaces that drive real business results. The clients say "It doesn't feel like outsourcing, but instead like we have our own remote developers." "They had great soft and hard skills and were full of ideas and drive!" I lead the fullstack and mobile development team at Itexus, a professional software development and consulting company focused on Fintech, Insurance, Healthcare, etc. I have 20+ years of experience in the .net architect development of web and mobile applications, .net, python, node.js, java developer as well as javascript, react .net, angular, AI frameworks and libraries. 👨‍💻.NET Full Stack Expertise .NET full stack – strong background in End-to-end development from database to UI using Microsoft stack .NET Core – deep expertise, cross-platform backend services .NET Angular – Full stack development on .NET backend and Angular frontend for enterprise-grade solutions .net core angular – Building complete systems with seamless backend–frontend integration .NET Core Angular – Scalable and secure web apps using .NET Core and Angular Angular .NET solutions – Using Angular for UI and .NET for API and business logic .net core developer – Proven experience delivering high-performance backend solutions using .NET Core .net core react – Building robust, scalable web applications with .NET Core APIs and React frontends c# .net developer – End-to-end development expertise using C# and the .NET ecosystem c# .net core – Advanced solutions built on C# with .NET Core for modern, cross-platform applications 👨‍💻 BACKEND Development Python: Expert in Python for server-side development Frameworks: Proficient in Django and Flask for building web applications Databases: Skilled in SQL, PostgreSQL, MySQL, and MongoDB for efficient data management Architecture: Experienced in applying MVC patterns for scalable applications APIs: Capable of integrating external services through REST and GraphQL 👨‍💻 FRONT END Development Proficient in HTML5, CSS responsive, JavaScript Experienced in React.js, Angular, Vue.js, react native, ionic, xamarin developer Responsive, cross-browser, ui/ux designer, ux/ui dashboard, ui ux designer app 👨‍💻AI TOOLS OpenAI API, DeepFace, ML/DL frameworks (TensorFlow, Keras, PyTorch, Scikit-learn), LangChain, Mistral, AgenticAI, Transformers RAG + custom AI tools: Document recognition and processing, Market Grabber, project management bots, AI for telephony, video/audio analysis Mobile App Development Native Mobile Development: Android, Kotlin, Java, iOS, Swift, KMP, KMM. Cross-Platform/Hybrid App Development: Flutter, Swift, Objective C, React Native, Xamarin, MAUI. General Expertise Website & Full Stack Development: Full stack development with ai .net full stack developer, .net software engineer, .net programmer, full stack developer, ai python full stack developer django, full stack web developer, full stack development, cms developer DevOps/DevSecOps: AWS, Azure, Docker, Kubernetes, GitLab-CI, Ansible, Terraform, etc Cross-platform app building with three.js, web application design, webflow web designer, website builders Integration tools: Data integration, websockets, ABP Framework, discord, Autotask Experienced in .net core web api, fullstack .net developer roles, with strong skills as a .net specialist. Skilled angular .net react developer, java developer with solid c sharp expertise. Worked on kogito for business automation, delivered ui ux-focused solutions. As an azure data engineer, handled scalable data pipelines. rust developer, python projects include backend developer tasks. Built app as a xamarin and web developer using java and javascript. Skilled in postgresql and web scrapping. Maintained legacy systems with .net webform. Collaborated with nft marketers, managed nft collab manage tasks. Full stack with react nodejs, modern react, including react typescript, react native developer roles. Acted as product owner in agile teams. Cloud deployments done on azure. Built interactive UIs using blazor. Why Choose us Microsoft certified talented developers and senior .net developer team High QA standards, including qa engineer roles Modern solutions: NFT programmer, metaverse, Microsoft .net, windows 10, Power Apps developer, SharePoint, market grabber Scalable team: full stack software developer, front end programmer, ios developer, ui ux designer Industries Banking, Trading, Cryptocurrency, Asset Management, Lending, Retail, Real Estate & Property Management, Food Delivery, Entertainment, Hospitality, Construction, Sports & Fitness, Travel & Tourism, Wellness, Medical Dashboard, Marketplace, E-commerce, Automotive, Human Resources, Education, E-learning, AI Assistants Seek new projects to put our .net ai, bring value to individuals, startups, companies.

Senior Full-Stack & Mobile Developer | React Native | Flutter | Next.js | Node.js | PostgreSQL Most founders waste almost 6 months on the wrong and unclear architecture. I help you skip that. I build AI-powered MVPs (Web & Mobile) that launch in 6-10 weeks - with clean architecture that doesn't fall apart when users arrive. 10+ years in production. $100K+ earned on Upwork. 100% Job Success I’m directly involved in full-stack development - architecture, backend, frontend, and native mobile apps. What I usually help with: 🚀 MVP Development: Turning ambiguous ideas into launch-ready products from scratch. 📱 Cross-Platform Mobile Apps: Crafting high-performance iOS and Android applications (React Native or Flutter) with smooth animations, background sync, and hardware/BLE integrations. ⚡ Full-Stack Web & AI Platforms: Building modern web frontends (React, Next.js) and secure backends (Node.js, Python/FastAPI, PostgreSQL) integrated with LLMs, vector databases, and structured data pipelines. ⚙️ Scalable Infrastructure: Making early architectural decisions, database modeling, and setting up stable cloud structures (Supabase, Firebase, AWS, GCP) that save time and budget later. I focus on building products that are: Simple to maintain Easy to extend Performance-driven and stable under real user load Selected results: FinTech: MVP delivered in 8 weeks for a transaction and asset-management tracking app. HealthTech & Pharmaceutical: Scalable multi-tenant platforms with clean data isolation and optimized infrastructure costs. Cross-Platform Dashboards: Real-time monitoring and analytics apps with active WebSocket states and live data updates. If you’re building an MVP, a data-heavy SaaS, or a mobile companion app and want clarity before committing to development, feel free to reach out. A short tech sync is often enough to define the right next step!