{ "name": "Zsolt Varjú", "title": "Software Developer", "headline": "Zsolt Varjú | Software Developer", "summary": "Hey there. I'm Zsolt, a developer from Čierna Voda in Slovakia, now living in Prague. I build software and I also run it in production. Today I look after a platform that delivers quality reports and data unavailability reports from Earth observation satellites on a project for the European Space Agency, aggregating validated data from ESA, legacy and third-party missions. I choose the approach, write the code, move the data, and keep the servers up.\n\nI started out testing other people's websites, which is where I learned to care about what happens after the deploy. Since then I've picked up the unglamorous half of the job: data pipelines, Linux, networking, backups. I lean on AI heavily in my daily work and I build with it too, mostly retrieval systems and self-hosted models. Outside work there's a homelab that has grown well past what I can justify, a motorcycle, and a ski season I never get enough of.", "shortDescription": "Zsolt Varjú is a software developer and platform operator based in Prague, building web applications end to end, designing ETL pipelines, and running the production infrastructure behind them.", "url": "https://zsoltvarju.com/", "language": "en", "updated": "2026-09-03", "generatedFrom": "src/messages/en.json", "localizedVersions": [ { "language": "Slovak", "code": "sk", "url": "https://zsoltvarju.com/sk" }, { "language": "Hungarian", "code": "hu", "url": "https://zsoltvarju.com/hu" } ], "location": { "label": "Prague, CZ", "city": "Prague", "country": "CZ", "origin": "Čierna Voda, SK" }, "inSoftwareSince": "2022", "contact": { "email": "dev@zsoltvarju.com", "linkedin": "https://www.linkedin.com/in/zsoltvarju/", "github": "https://github.com/zsoolti8917", "website": "https://zsoltvarju.com/" }, "current": { "role": "Software Developer at Serco, Prague", "detail": "I own and run a platform for the European Space Agency that delivers quality reports and data unavailability reports from Earth observation satellites: the code, the data pipelines, CI/CD, and the servers it runs on." }, "experience": [ { "company": "Serco Czech Republic s.r.o.", "title": "Software Developer", "location": "Prague", "dates": "Feb 2025 - Present", "responsibilities": [ { "area": "End-to-End Ownership", "description": "Own and run, end to end, a platform for the European Space Agency that delivers quality reports and data unavailability reports from Earth observation satellites, aggregating validated data from ESA, legacy and third-party missions." }, { "area": "Solution Design & Delivery", "description": "Choose the approach, technologies and architecture for new work, present it, build it, take it through UAT to production, and keep it running: monitoring, fixes, patches and backups." }, { "area": "Development", "description": "Develop the frontend, the backend and the data ingestion pipelines, and maintain the automation scripts around them." }, { "area": "Operations & Security", "description": "Administer the platform's two Ubuntu servers: containers, CI/CD, updates, backups, access control and regular vulnerability remediation under formal change control." }, { "area": "Server Migration", "description": "Led the migration of a legacy service from Ubuntu 18.04 to a new Ubuntu 24.04 LTS server: dockerised the legacy codebase so it runs on the new host, closed the outstanding vulnerability findings and brought the server under regular patching, and replaced a manual multi-step deployment with a single automated, zero-downtime release." }, { "area": "Performance & Code Quality", "description": "Led a phased frontend quality programme: vendor bundle cut by roughly three quarters, JavaScript payload down a third, CSS down more than half, unnecessary re-renders reduced by 80%." }, { "area": "Stakeholder Coordination", "description": "Work directly with the mission teams and IT on requirements, solution proposals, bug reports, change records and estimates." } ], "skills": [ "React", "Node.js", "Python", "Docker", "Linux", "Bash", "CI/CD", "Jenkins" ] }, { "company": "Galileo Corporation s.r.o", "title": "Quality Assurance Tester", "location": "Remote", "dates": "2022 - 2025", "responsibilities": [ { "area": "Functionality Testing", "description": "Conducting thorough manual testing of web pages to verify that all features operate correctly across various browsers and devices. Identifying and reporting discrepancies or bugs promptly." }, { "area": "Visual Consistency", "description": "Assessing the visual appearance of web pages to ensure they match the provided graphic design specifications. Communicating deviations to the relevant team members and providing detailed feedback for necessary corrections." }, { "area": "Quality Assurance", "description": "Maintaining high standards of quality by rigorously testing web pages, ensuring they meet required specifications and user expectations." }, { "area": "Communication", "description": "Collaborating effectively with designers, developers, and project managers to address issues found during testing and offering suggestions for improvements and clarifications." }, { "area": "Remote Work", "description": "Managing all tasks independently while adhering to strict deadlines and utilizing effective time management skills to complete tasks efficiently and accurately." }, { "area": "Documentation", "description": "Maintaining detailed records of test results, issues identified, and corrective actions taken, and providing comprehensive reports to relevant stakeholders." } ], "skills": [ "HTML", "CSS", "JavaScript", "Cross-Browser Testing", "Bug Tracking", "Remote Collaboration", "Time Management" ] } ], "projects": [ { "name": "Self-Hosted RAG Search", "description": "A retrieval-augmented search system over a local document collection, built to answer questions with citations, and to stay quiet when the evidence isn't there.", "tech": [ "Python", "Qdrant", "bge-m3", "LangChain", "Docker" ], "url": null, "repository": null, "highlights": [ "Hybrid retrieval combining BM25 keyword search with vector similarity", "bge-m3 embeddings stored in a Qdrant vector database", "Every answer grounded in retrieved passages, with inline citations", "Explicit abstention when no supporting passage is found, instead of a plausible guess", "Runs fully self-hosted, with local models as an alternative to hosted APIs", "Cost modelling comparing hosted API inference against running a GPU yourself" ] }, { "name": "Coffece (coffece.sk)", "description": "A bilingual (SK/EN) marketing and ordering site for an office coffee delivery brand: product pages, FAQ, testimonial carousel, and contact flow, with full SEO metadata.", "tech": [ "Next.js", "TypeScript", "TailwindCSS", "next-intl", "Framer Motion" ], "url": "https://coffece.sk", "repository": null, "highlights": [ "Fully localized SK/EN routing powered by next-intl", "Product and offering pages for office coffee delivery", "FAQ section and a testimonial carousel", "Contact and ordering flow with validated forms and e-mail delivery", "Complete SEO metadata including Open Graph tags", "Smooth Framer Motion animations and dark mode support" ] }, { "name": "IDT PLUS STAV (idtplusstav.sk)", "description": "Complete digital operations for a Slovak diamond drilling and concrete cutting company: a self-hosted marketing website, business email, invoicing configured for Slovak VAT rules, plus paid search and SEO.", "tech": [ "Next.js", "TypeScript", "TailwindCSS", "MDX" ], "url": "https://idtplusstav.sk", "repository": null, "highlights": [ "Dedicated pages for each drilling and cutting service, with pricing and FAQ", "Project news section built on MDX articles", "Extensive references section showcasing completed projects", "Quote request form with validation and e-mail delivery", "Self-hosted deployment on a Dokku-managed server", "Google Workspace with DKIM-authenticated business email", "Invoicing set up for Slovak VAT reverse charge", "Google Ads campaigns and ongoing SEO" ] }, { "name": "B2B Wholesale Ordering Portal", "description": "A private B2B ordering portal implemented for a Slovak fresh-produce wholesaler, now in production. Features tiered customer pricing, a login-only catalog with hidden prices, two-warehouse inventory, decimal quantities for weighted goods, and integrated invoicing.", "tech": [ "WooCommerce", "B2BKing", "Stock Locations", "SuperFaktúra" ], "url": null, "repository": null, "highlights": [ "Tiered customer pricing with per-group price lists", "Login-only catalog with prices hidden from the public", "Inventory tracked across two warehouses", "Decimal quantities for weighted goods, such as ordering by the kilogram", "Integrated invoicing via SuperFaktúra" ] }, { "name": "Lemma: Vocabulary Scanner", "description": "A mobile app that turns a photo of a printed page into vocabulary cards. Point the camera at text, and it pulls out the words worth learning and schedules them for review.", "tech": [ "React Native", "Expo", "Vision models", "FSRS" ], "url": null, "repository": null, "highlights": [ "Camera capture with a vision-language model detection pipeline", "Word extraction and lemmatisation from printed pages", "FSRS spaced-repetition scheduling, so reviews land when you are about to forget", "Offline-friendly local storage", "Cross-platform from a single React Native and Expo codebase", "Specced through to v1.1" ] }, { "name": "Personal Infrastructure & Homelab", "description": "A personal VPS and home server run with production habits: private networking, atomic zero-downtime deploys, and a stack of self-hosted services.", "tech": [ "Linux", "Docker", "WireGuard", "Tailscale", "CI/CD" ], "url": null, "repository": null, "highlights": [ "WireGuard private networking linking the VPS and the home network", "Atomic zero-downtime deployments, with instant rollback", "Tailscale mesh access to home services from anywhere", "Docker-based NAS services including media streaming and camera recording", "Self-healing service recovery and scheduled backups", "Remote development driven from a phone when needed" ] }, { "name": "Tech Blog — zsoltvarju.dev", "description": "A personal engineering blog in English: software development, self-hosted infrastructure, testing, and AI — every post grounded in something that actually happened.", "tech": [ "Jekyll", "Markdown", "RSS", "Netlify" ], "url": "https://zsoltvarju.dev", "repository": null, "highlights": [ "Practical step-by-step guides, like deploying Dokku on a VPS", "Debugging stories that show the investigation, not just the fix", "AI explored hands-on — project ideas and tooling, not hot takes", "A static site generated with Jekyll, served from a CDN", "An RSS feed, for readers and machines alike", "Tagged and searchable, written in plain English" ] }, { "name": "Multi Photo Cropper", "description": "A personal tool for digitizing family photo albums. Scan several prints at once on a flatbed, and it finds each photo on the sheet, lets you fine-tune the boxes, and exports every crop at full resolution as a ZIP.", "tech": [ "React", "TypeScript", "Vite", "FastAPI", "OpenCV", "ONNX Runtime", "Docker" ], "url": null, "repository": null, "highlights": [ "Automatic photo region detection running entirely in the browser", "An optional self-hosted backend that merges four detection strategies by IoU consensus voting", "Local CPU inference of a YOLOv8-nano ONNX model, with no cloud service and no API keys", "Texture and color histogram validation that separates a real photo from blank scanner background", "Per-region skew analysis with deskew and perspective correction", "Full manual control: draw, drag, resize with eight handles, zoom, pan, undo history, and keyboard shortcuts", "A “photos per scan” hint that constrains the detector to the expected number of prints", "Crops re-extracted at full source resolution and exported together as a ZIP", "Automatic fallback to the in-browser detector whenever the backend is offline" ] }, { "name": "Municipal Website Migrations", "description": "Content migration and restructuring for five Slovak municipal websites, including bilingual Slovak and Hungarian content.", "tech": [ "Virgo / GCM Cloud CMS" ], "url": null, "repository": null, "highlights": [ "Complete content inventories of the legacy websites", "Page trees restructured to fit the new CMS", "Migration of documents, official notices, contracts, and image galleries", "Bilingual Slovak and Hungarian language mutations", "Post-migration audits comparing the old and new sites page by page" ] }, { "name": "InfoMap SK: Master's Thesis", "description": "A full-stack application for visualising Slovak open data on an interactive map, built as my master's thesis project. The public site is no longer online; the source remains available.", "tech": [ "React", "Node.js", "Express", "MongoDB", "TailwindCSS" ], "url": null, "repository": "https://github.com/zsoolti8917/InfoMapSK-frontend", "highlights": [ "Interactive map of Slovakia with region, district, and city/village selection", "Visualization of demographic data using various chart types", "Multiple data categories: Population, Economic Activity, Agriculture, and Organizational Statistics", "Search functionality for specific locations", "Responsive design optimized for various devices", "Accessibility features following WCAG 2.1 guidelines", "Contact form for user feedback and inquiries" ] }, { "name": "Garden Bros Website", "description": "A website for a gardening company, built with Next.js, styled with Tailwind CSS, and managed through Strapi CMS. Features responsive design, dynamic content generation, and deployment on Vercel.", "tech": [ "Next.js", "Tailwind CSS", "Strapi CMS", "Vercel", "VPS", "Dokku", "PostgreSQL" ], "url": null, "repository": "https://github.com/zsoolti8917/garden-bros-frontend", "highlights": [ "Responsive main page with dynamic components", "Fully-featured contact page and FAQ section", "Blog with author-written posts", "Dynamic page generation", "Content management through Strapi CMS" ] }, { "name": "Alza Dni Kupónový Filter", "description": "A Chrome extension that helps users filter products during Alza Days sales by various coupon codes, making it easier to find the best discounts on Alza.sk.", "tech": [ "JavaScript", "Chrome Extension API", "HTML", "CSS" ], "url": "https://github.com/zsoolti8917/Alza", "repository": "https://github.com/zsoolti8917/Alza", "highlights": [ "Filtering products by coupon codes (5%, 10%, 15%, 20%, 25%, 30%, 50%)", "Option to filter only currently displayed products or load all products", "Simple and clear user interface", "Quick filter removal with one click" ] } ], "skills": { "groups": [ { "label": "Languages & frameworks", "items": [ "TypeScript", "JavaScript", "Python", "Bash", "SQL", "React", "Next.js" ] }, { "label": "Backend & data", "items": [ "Node.js", "Express", "REST API", "Apache Solr", "Neo4j", "RabbitMQ", "Tika", "PostgreSQL", "MongoDB", "Headless CMS" ] }, { "label": "Infra & ops", "items": [ "Docker", "Kubernetes", "Jenkins", "GitHub Actions", "Azure", "Linux", "nginx", "Dokku", "WireGuard", "Tailscale" ] }, { "label": "Tools", "items": [ "Git", "Postman", "Figma" ] } ], "ai": { "label": "AI & LLM", "items": [ "RAG architecture", "Embeddings", "Vector search", "Qdrant", "Hybrid retrieval", "Prompt engineering", "Claude Code", "Codex", "OpenRouter", "LangChain / LangSmith", "Self-hosted models" ] }, "exploratory": { "label": "Tried out / Used in school", "items": [ "Storybook", "Java", "OOP", "AdobeXD", "Laravel", "Unity", "Blender", "GraphQL", "C#" ] } }, "education": [], "certifications": [ { "name": "Certified Kubernetes Administrator (CKA)", "issuer": "Linux Foundation / CNCF", "date": null }, { "name": "Ubuntu Linux Professional Certificate", "issuer": "Canonical", "date": "Apr 2025" }, { "name": "Learning Bash Scripting", "issuer": "LinkedIn Learning", "date": "Jul 2025" }, { "name": "Basics of ABAP Programming on SAP BTP", "issuer": "SAP", "date": "Oct 2024" }, { "name": "AWS Academy Graduate, Cloud Foundations", "issuer": "AWS Academy", "date": "Jul 2022" } ], "languages": [ { "name": "Hungarian", "level": "native" }, { "name": "Slovak", "level": "fluent" }, { "name": "Czech", "level": "fluent" }, { "name": "English", "level": "fluent" } ], "documents": { "cvMarkdown": "https://zsoltvarju.com/cv.md", "llmsTxt": "https://zsoltvarju.com/llms.txt", "cvPdf": { "english": "https://zsoltvarju.com/Varju-CV-EN.pdf", "slovak": "https://zsoltvarju.com/Varju-CV-SK.pdf", "hungarian": "https://zsoltvarju.com/Varju-CV-HU.pdf" } } }