Slavik C.

Senior Full-Stack Engineer - React, Node.js, TypeScript, Next.js SaaS

🟢 Expert-vetted, top 1% Full Stack Developer on Upwork. $1M+ earned, 18,000+ hours, 100% job success. Pragmatic approach & clear communication. I help founders build an MVP, or to improve and scale software that's already live. If your plan is heavier than it needs to be, I'll say so. ❇️ Projects I'm personally passionate about: 💡 A SaaS platform for construction pros, ProCodes Companion, in React and Node.js with a GPT-4 chatbot grounded in their own uploaded building codes and zoning docs rather than general model knowledge. Three Stripe tiers, team management, admin dashboards, and an iframe embed so clients can drop it into their own site. 💡 A GDPR-first AI platform for schools, now used by around 350 across Ireland and the UK. Its privacy tokenisation layer swaps names, PPS numbers, and addresses for session-scoped tokens before any query reaches the model, then restores them on the way back, so the AI never sees a real identity. 💡 A hospitality hiring marketplace for web, iOS, and Android, built full stack in React and React Native. Job seekers build profiles, upload CVs, and manage availability through a built-in calendar. Employers post roles on tiered Stripe subscriptions. Now carrying 15,000+ registered businesses and 19,000+ open positions. 💡 An adaptive SAT/ACT prep platform in React, Node.js, and Python, powered by the OpenAI API and built with input from Stanford PhDs. It turns raw practice scores into a learning path that adjusts after every session. EdTech is my jam. 💡 An AI RAG document search tool in Python and LangChain, wired straight into SharePoint and Dynamics 365. It indexed 300,000+ internal files and cut research time by 75%. 💡 A HIPAA-compliant AI note-taking tool in Node.js and Whisper on a secure cloud backend. It turns a psychiatrist's spoken session into a structured clinical note and saves hours of paperwork daily. ~ How I work ~ My team and I handle product development from start to finish: business idea, design, deployment, testing. 100% success over more than 18,000 hours. My longest current engagement is going on two years with the same client. We build software that's GDPR, HIPAA, SOC 2, PCI-DSS, and CCPA compliant. I build that in from day one because retrofitting it costs three times as much. ~ Stack ~ My default for new builds is TypeScript end to end: React and Next.js on the frontend, Node.js on the backend, PostgreSQL or Supabase for data. I use Python where it fits better, usually FastAPI or Django for AI and data-heavy services, and Firebase where the project already lives there. AI goes into that same codebase rather than a separate bolted-on service. I work with OpenAI, Anthropic Claude, Gemini, Mistral, and Llama, orchestrate through LangChain, and ground answers in real data with Pinecone or Elasticsearch. I build RAG systems, autonomous AI agents, chatbots, and multi-step workflows. For mobile app compatibility I build in React Native, with Swift or Kotlin where a native module is needed. I also work in PHP, Laravel, and WordPress on legacy or client-mandated stacks. 🔹 Frontend: React, Next.js, TypeScript, JavaScript, Tailwind, HTML5, CSS3 🔹 Backend: Node.js, Express, Python, FastAPI, Django, Flask 🔹 Mobile: React Native, Swift, Kotlin 🔹 Databases: PostgreSQL, Supabase, MongoDB, MySQL, Redis, Firebase 🔹 AI and LLM: OpenAI, Anthropic Claude, Gemini, Llama, Mistral, LangChain, RAG 🔹 Vector search: Pinecone, Elasticsearch 🔹 Voice: Whisper, ElevenLabs, VAPI 🔹 Cloud and DevOps: AWS, Azure, GCP, Vercel, Git 🔹 APIs and integrations: REST, Stripe, Twilio, SharePoint, Dynamics 365 🔹 Compliance: GDPR, HIPAA, SOC 2, PCI-DSS, CCPA 🟢 Building a SaaS platform, MVP, or internal tool for your company? Send me the brief. You'll get an honest read on scope and timeline before you commit. Talk soon