Full Stack & AI Developer — Available for new projects
Web and AI products that deliver results
I design, build, and ship Next.js applications that are fast, accessible, and engineered to convert. Trusted by Euroclear France, Isotoner, Balzac Paris, and Tartine & Chocolat.
About
FreelanceFullStackDeveloperbasedinParis,IbuildwebproductsandAIfeaturesthatactuallyshiptoproduction.SpecializinginNext.js,ReactandTypeScript,Ihelpstartups,scale-upsandlargecompaniesturnambitiousideasintorobustapplications,frommodernUIdesigntobackenddevelopmentwithNode.js,NestJSandPostgreSQL,allthewaytodeploymentonVercelordedicatedinfrastructure.
PATRICK BARTOSIK · PARIS, FR
My work now spans two practices. Software engineering: server-side rendering, REST and GraphQL APIs, microservices architectures. And artificial intelligence: LLM integration (Claude, OpenAI, Azure AI Foundry), autonomous agents, and RAG knowledge bases over your private data. The same standards apply everywhere: clean code, accessibility (WCAG), technical SEO and Core Web Vitals, for high-performing products that convert and rank durably on Google.
Selected Work
Services
AI features that actually ship to production, not demos.
Integrating language models (Claude, GPT) into your products: conversational interfaces, content generation, data extraction, and intelligent features shipped to production.
Building autonomous agents and automated workflows that run your business processes: customer support, lead qualification, document processing.
Turn your documents into a knowledge base you can query in plain language: semantic search, sourced and up-to-date answers, without hallucinations.
Intelligent voice agents built with Vapi that answer the phone, qualify calls, book appointments, and run your reception desk 24/7.
Connected phygital experiences: NFC cards and smart QR codes that trigger automations — Google reviews, menus, business cards, tracked campaigns.
Robust web products, from front-end to infrastructure.
A site that loads in under a second, ranks on Google, and turns visitors into customers. Custom-built with Next.js and React — no templates.
Shopify Plus stores and custom e-commerce. I worked on migrations for Isotoner, Balzac Paris, Tartine & Chocolat, and Qwetch: replatforming without traffic loss, ERP integrations, and purchase flows that convert.
Your SaaS from idea to launch: authentication, Stripe subscriptions, dashboards. An architecture designed from day one to handle your user base growing.
The backend that connects your tools together: documented REST/GraphQL APIs, webhooks, ERP/CRM synchronization. Robust, secure, and built for your teams to build on.
Business goals, audience, constraints: the project is scoped before the first line of code.
UX/UI mockups and technical architecture, validated together before development.
Iterative sprints, regular demos, and code continuously accessible on Git.
Testing, production rollout, monitoring, and knowledge transfer.
Testimonials
Patrick demonstrated exceptional expertise as a full-stack developer at W3lead. His technical mastery and ability to deliver robust solutions were decisive for our e-commerce projects. A true asset to the team.
Gary Trojanowski
CEO & Founder, W3lead
I collaborate with entrepreneurs, early-stage and growth-stage startups, scale-ups, SMBs and large companies looking for a freelance Full Stack Developer to build custom web applications. My clients are mainly based in France (Paris, Lyon, Bordeaux), but I also work remotely with teams across Europe and North America. I can act as a tech lead on a project from scratch or join an existing team for short-term reinforcement, on a time & materials or fixed-price basis.