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Full-Stack Software Developer Full-stack software developer with professional experience building scalable, reliable, and maintainable applications using .NET and C#. I specialize in backend development, microservices architecture, cloud-native solutions, and database design, with hands-on experience using Docker, Kubernetes, SQL, and NoSQL technologies. My background includes both software development and QA engineering, giving me a strong focus on code quality, automated testing, and long-term maintainability. I have worked in Agile teams throughout the full software development lifecycle, collaborating closely with stakeholders while also successfully delivering projects independently from concept to deployment. I am proficient in .NET, C#, Python, Ruby, C, and C++, and I leverage modern AI-assisted development tools to improve productivity, accelerate delivery, and enhance code quality while maintaining full engineering oversight and adherence to industry best practices. Core Skills: .NET / C# Full-Stack & Backend Development Microservices Architecture Docker & Kubernetes REST API Development SQL & NoSQL Databases Python, Ruby, C, C++ Automated Testing & QA Agile Development I focus on delivering clean, maintainable, and high-quality software solutions that solve business problems and scale with future growth.

➤ $1.8M+/year projected savings - AI document search (RAG) for a $300M/year NYC infrastructure contractor: teams search 10,000+ pages per project, daily search time cut from 60 minutes to 10 (Azure, OpenAI). ➤ 2,400+ AI recommendations - 92% mobile adoption, 8.1 chats/user (Next.js, Django, Flutter). ➤ 75% infrastructure cost cut - migrated a $300M/year brand to serverless microservices (AWS, Node.js/TypeScript). ➤ 300k+ monthly users - production ordering platform with payments, subscriptions, and admin dashboard. I'm Luka, a senior full-stack and AI engineer. I own the full stack and the full product process end to end: scoping, UI/UX design (Figma), frontend, backend, web application and mobile application development, AI integration, deployment, and post-launch improvements. From scratch or inside your existing app, from prototype to production. WHAT I BUILD • AI agents and agentic workflows - multi-agent systems, tool use, MCP servers, AI automation and workflow automation that replace manual work • AI chatbot development and AI assistants - customer support chatbot, internal knowledge base assistant, WhatsApp and Telegram bots • RAG and AI document search - semantic search, vector search, embeddings, data extraction, hallucination control and evals • AI voice agents and voice assistants - real-time voice, Whisper, ElevenLabs, Deepgram, Twilio • AI integrations into existing products - OpenAI, Anthropic Claude, Gemini; AI features added to your current software • AI-powered SaaS platform and MVP development - user authentication, payments (Stripe), subscription billing, admin panel, dashboards • Web app development - React, Next.js, TypeScript, Tailwind CSS; fast, scalable, real-time • Mobile app development - React Native (Expo) and Flutter, iOS + Android, App Store launch included • Internal tools, CRM and dashboard builds, customer portals, marketplace and booking platforms • Backend and API development - Node.js, Python (FastAPI, Django), REST API, webhooks, API integration with third-party services SELECTED PROJECTS • Spinio - AI recommendation chatbot for the UK market with 95%+ recommendation accuracy; helps users find the right option through natural language search • Leelou AI - AI voice coaching chatbot for TNM Coaching: instant leadership coaching built on the company's framework, helped them close a 200+ employee enterprise client • SEO AI Platform - AI agents for a large SEO company: content generation, data analysis, and text/image compliance checks; active long-term build, new features shipped every sprint (under NDA) • Ergo Global - private AI customer support system: website chat, internal app chat, and Outlook inbox automation, faster responses while keeping sensitive customer messages private • Juggle Ease - multilingual AI voice assistant inside a family mobile app; users talk to the app and complete tasks hands-free, with responses under 0.5 seconds • Rooost - AI accommodation concierge that gives business travelers local recommendations based on where they are staying STACK Frontend: React, Next.js, TypeScript, JavaScript, Tailwind CSS, Figma-to-code Backend: Node.js, Python, FastAPI, Django, REST APIs, websockets, webhooks Mobile: React Native, Expo, Flutter AI/LLM: OpenAI (GPT, ChatGPT), Anthropic Claude, Gemini, LangChain, prompt engineering, MCP, multi-agent orchestration, LLM evals Data: PostgreSQL, Supabase (Postgres), MongoDB, MySQL, Redis, vector databases (Pinecone, pgvector, Qdrant) Cloud: AWS, Azure, GCP, Vercel, Docker, CI/CD Integrations: Stripe, Twilio, Firebase, WhatsApp, Telegram, HubSpot, Salesforce AI-assisted development: Claude Code, Cursor — with senior-engineer review on every line HOW I WORK My approach is simple, but uncommon. I start each project by setting KPI goals with you and scoping the requirements. Then I dive into development. 1–2 weeks to a proof of concept, 6–8 weeks to a production MVP. Once development is completed, I don't disappear: I stick around for 4 more weeks COMPLETELY FREE to optimize the project until we hit the KPI goals we set, and fix any bugs. I take on 1–2 new builds per month to preserve quality. Message me with your goal and if we're a good fit we can get on a call!

As a software engineer with over 10 years of experience, I have developed expertise in designing and implementing enterprise-grade software solutions. My experience spans a variety of industries and sectors, including teleco, finance, and government.  One of my key strengths is my ability to understand complex business requirements and translate them into effective technical solutions. As a solution architect, I have been responsible for designing software architectures, selecting appropriate technologies and frameworks, and guiding development teams in implementing these architectures. I have also worked as a consultant, advising clients on best practices and helping them implement software solutions that meet their business needs. Throughout my career, I have gained expertise in a range of technologies, including Java, Spring, Hibernate, Quarkus. I am familiar with Agile and DevOps methodologies, and I have experience working with tools such as Git, Jenkins, Docker, and Kubernetes. In addition to my technical expertise, I am a strong communicator and team player. I enjoy collaborating with colleagues, sharing knowledge, and mentoring junior developers. I am comfortable working in both remote and on-site environments, and I thrive in fast-paced, dynamic work environments. Overall, I am a results-oriented software engineer with a proven track record of delivering high-quality software solutions that meet business needs. I am passionate about software development and committed to staying up-to-date with the latest technologies and industry trends.

I will skip the hero section and tell you directly what I can do for you: • stable deployments that don’t break on Fridays • consistent, reproducible environments (no more “works on my machine”) • clean CI/CD pipelines with fast, reliable builds and deployments • zero-drift infrastructure with clear IaC discipline • fewer incidents and faster recovery when something goes wrong • simple, maintainable setups with clear documentation • a platform the whole team can trust and build on • faster onboarding for new engineers (everything predictable, documented and automated) • disaster-recovery flows that actually work (Btrfs snapshots, backups and reliable restore paths) • smoother day-to-day operations so your team focuses on building, not firefighting Hi — you’re still here? Thank you. If this resonates with you, we’ll be a good fit. Let’s talk. 11 successful Upwork projects and counting — 5★ reviews and long-term clients. Here are more details about my work — I know you want to know more about me. I follow best DevOps practices to build stable cloud infrastructure using Containers (Docker, Docker Compose), Kubernetes (Rancher, K3s, RKE2, MicroK8s), Infrastructure as Code / IaC (Terraform, OpenTofu) and CI/CD (GitLab CI/CD, GitHub Actions, Rancher Fleet) — deployed on AWS, GCP and Hetzner Cloud. With 20+ years of engineering experience, I deliver clean, reliable and reproducible environments that behave consistently under load. My work spans greenfield builds, modernization of legacy systems and stabilizing fragile or inconsistent environments by improving architecture, tightening IaC discipline, restructuring Kubernetes workloads and enforcing clean CI/CD patterns. What I work with: • Kubernetes (Rancher, K3s, RKE2, MicroK8s, GKE) • Infrastructure as Code / IaC (Terraform, OpenTofu — clean, reproducible infrastructure) • Containers (Docker, Docker Compose) • CI/CD (GitLab CI/CD, GitHub Actions, Rancher Fleet) • Legacy monoliths, VMs, custom setups → containers / cloud migration • Observability (Fluent Bit, Stackdriver, GCP Logging, monitoring, alerts) • Environment design (dev → stage → prod, automation, separation, promotion flow) • Troubleshooting hard-to-reproduce infrastructure issues I expect every client to bring a slightly different stack and workflow. That’s what keeps this work interesting. If your tools aren’t on this list, that’s completely fine. I’m always ready to adapt, learn, and grow with you through real project work. Here’s a bonus for the end — because if you’ve read this far, you’re clearly a patient person. I don’t start with AI, LangChain, RAG pipelines, vector databases or any other buzzword stack, because I don’t want to attract the wrong crowd. The truth is, AI is not the foundation. It’s just a layer your developers will build on top of stable infrastructure. That’s where I come in. And after 20+ years in different roles — from junior coder to Head of Software Development (CTO-level responsibilities) — I know how to build a platform that makes every layer above it stronger, including AI.

" Matej was great to work with. He fully understands the development cycle and how to work with a team. When laying out tasks he easily understands what needs to be accomplished and has great ideas for improvements and efficiency. " Hello and Thank you for considering me for your contract. I am a full stack developer, with more than 13 years of experience. I started in the Casino industry, and I grew to Senior Architect on multiplatform casino games and backend. I have experience with both frontend and backend code architecture and my code is still working flawlessly after all these years. When I code, there are a few things that I value the most: 1. Simplicity 2. Efficiency 3. Communication I am able to quickly adapt to new environments, and new codebases. When designing a system, all of the best practices are honored. Testing, CLEAN architecture, understandable even for non technical persons. My greatest skill is thinking many steps ahead. Like in chess, who is able to outthink his opponent wins. In my case, and I guess that comes with experience, I predict future scenarios so your code is always ready to scale when the time comes. .Net C# Java Spring Php Reactphp Svelte Flutter Dart Rive iOS Android Node.js microservices Firebase MySql MongoDb Angular ... Looking forward to work together ! Matej 🌳🌲🌴

Greetings 👋 I’m a Senior Full Stack Java Spring Boot Developer and a Certified AWS DevOps Engineer with more than 10 years of professional experience in end-to-end fullstack development. My background includes Java based backend systems using Spring Boot, Spring MVC, and Spring Cloud, and in building modern fullstack apps with React. My work spans across healthcare, insurance, and automation platforms. 📌 What I Provide 💼 🔹 Complete development lifecycle: planning, coding, testing, deployment, and maintenance 🔹 AWS and Java certified expertise 🔹 Implementation of DevOps practices and CI/CD pipelines 🔹 Cloud cost-efficiency strategies 🔹 Application performance enhancement 🔹 Rapid MVP development to bring your concept to life 📌 Why Collaborate with Me 🤝 🔹 10+ years of hands-on experience in Java and DevOps engineering 🔹 Specialized knowledge in domains like Healthcare and AdTech 🔹 Strong commitment to high code quality and reliability Fullstack / Frontend Capabilities ⚛️ As a Full Stack Java Spring developer, I build engaging and scalable applications by integrating modern frontends - React.js, Next.js, and Vue.js - with robust Spring Boot and Java-based backends. I follow fullstack best practices and deliver clean UI using HTML, CSS, and Tailwind CSS. Back End Expertise ⚙️ Working with Java since version 6 through 21, I utilize frameworks such as Spring Boot, Spring MVC, Spring Cloud, Spring Batch and Spring Security to build scalable services. DevOps & AWS Experience ☁️ With 8+ years in AWS environments and certifications in both DevOps Architecture and Development, I specialize in serverless and containerized solutions using AWS Lambda, Docker, Kubernetes, RDS, and Landing Zone - ensuring scalability and zero-downtime deployments. Database Skills 💾 I’m proficient in relational databases like PostgreSQL, MySQL, and SQL Server. Also skilled with NoSQL systems including Redis, MongoDB (DocumentDB), Aerospike, DynamoDB, and OpenSearch (ElasticSearch). For analytics, I work with Amazon Redshift. API Integration 🌐 Skilled in REST, SOAP, Swagger, and OpenAPI 3 for seamless service integration. Performance Tuning 🚀 Utilizing tools like JMeter, Gatling, AWS X-Ray, and JProfiler to optimize speed and resource usage. Messaging Systems ✉️ Experienced in asynchronous communication with Apache Kafka, Amazon SQS/SNS, and RabbitMQ. Desktop GUI Development 🖥️ Developing sleek and functional desktop interfaces with JavaFX and FXML. Let’s connect and talk about your goals! 🚀