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Sergiy Mirochnyk

Sergiy Mirochnyk

Senior Full-Stack Engineer · AI / LLM Engineer

Web applications end to end — interface, API, data, deployment — plus AI agents, RAG and automation that hold up in production.

mirochnyk.sergiy@gmail.com +33 7 54 38 67 68 github.com/SergeMiro linkedin/in/sergemiro smiro.dev ask my AI avatar Dijon, France · French citizen · remote or hybrid

Summary

Senior full-stack engineer, 9 years building and running production web applications end to end — interface, API, database, deployment and monitoring. Core stack React / Next.js / TypeScript / Node.js / Python with PostgreSQL / SQL Server. Since 2023 I have shipped applied AI in production: multi-agent systems, RAG over company data, LLM fine-tuning and n8n automation — with tests, evaluations, monitoring and cost controls around them. I provision, secure and operate what I ship on Linux VPS with Docker, Nginx and CI/CD: an npm failover proxy merged upstream, a façade contractor's platform in production, a Telegram commerce app. French C2.

Professional Experience

Full-Stack Developer & AI Engineer

Sep 2023 — Present

FIMAINFO — Software development & cloud solutions·Dijon, France

  • Designed and shipped multi-agent AI systems for call-centre campaigns: an executor agent does the work, a reviewer agent scores it, and the loop repeats until the score reaches 90%. Cut back-office work by ~80% — about 30 hours a week per team covered. OpenAI API · Anthropic Claude API
  • Built RAG search over internal business knowledge and exposed company data to agents through MCP-style tools and REST APIs, with per-role access control (RBAC). embeddings · pgvector · Qdrant
  • Delivered full-stack internal products end to end: responsive React / Tailwind interfaces, Node.js / Express APIs, SQL Server / T-SQL across four estates, Jest tests, CI/CD and production deployment.
  • Fine-tuned open-weight LLMs and served them from in-house GPU servers behind REST APIs — data stays on company hardware and token spend drops; added routing between light and heavy models. Unsloth · LoRA / QLoRA · Llama · Mistral
  • Automated recurring back-office with n8n: email parsing, ticket routing, invoicing, compliance filings, notifications. Added monitoring, SLA alerting and anomaly detection. Grafana · Metabase
  • Introduced an AI-assisted development workflow with spec-driven prompts and reviewer gates before merge — shorter cycles without giving up code review, tests or OWASP checks. Claude Code · Cursor · Copilot

Web Developer

Aug 2022 — Aug 2023

Novileads Co.·Ukraine · remote

  • Built responsive marketing sites and web applications from Figma mockups, and shared component libraries with the back-end developers and designers. HTML5 · CSS3 · JavaScript
  • Front-end performance and cross-device compatibility; technical SEO and Core Web Vitals checked on delivery.

Web Developer — French Foreign Legion

May 2017 — May 2021

French Foreign Legion — Képi Blanc magazine & other Legion sites·France

  • Built and maintained site components for Képi Blanc magazine and other Legion sites; ran the content with the editorial team, plus technical SEO, social integrations and performance work.

IT Technician

Oct 2011 — May 2017

French Foreign Legion — 1st R.E.G. / 1st R.E.·France

  • Installed, configured and maintained hardware and software fleets for operational units, with L1/L2 support for their users.
  • Network security: firewall and antivirus administration, system hardening.

Selected Projects

LLM Failover Proxy open source · npm · 2026

One OpenAI-compatible endpoint that switches model when a provider fails, rate-limits or slows down — without breaking a live stream. 12 commits and +1,638 lines merged upstream, published as v1.8.0. Node.js 22 · SSE · zero runtime dependencies

Extranet Fimainfo work · internal platform · 2026

One internal platform for telephony, campaigns, messaging, BI and an AI assistant: 5 services, ~60 screens, 4 SQL Server estates, ~786 commits over 17 months. Next.js 15.5 · React 19 · Express · SQL Server ×4 · FastAPI · Qdrant · RAG

ASCoFacade production · client · 2026

Public SEO site and 4 role portals behind one login — office, clients, sub-contractors, field crews — plus 3 AI jobs, none of them a chatbot. Next.js 16 · React 19 · Supabase RLS · Server Actions · Vercel

SimplifyEU AI back-office · 2026

Finds duplicate invoices, unused subscriptions and missed deadlines across 4 Python services. Next.js 16 · FastAPI · Celery + Redis · Docker + Traefik

Way2Buy Mini App telegram · product · 2026

Telegram Mini App for sales, cashback, discounts, margin tracking and AI reports. Node.js + Express · SQLite · idempotent jobs · 81 tests

Earnings trading bot research lab · 2026

Personal multi-agent lab for earnings research, scoring and fixed risk rules. Not financial advice. Python 3.12 · SQLAlchemy 2 · APScheduler · Docker