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Hi, I'm

JansenFerreira

Full Stack Developer. I build fast, fluid and memorable web experiences, from the database to the animation.

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About.

Jansen Ferreira

I'm a full stack developer with 3 years of hands-on experience shipping production applications, focused on React and TypeScript. I've worked remotely for European startups and research institutions in Poland and Germany, evolving scientific and industrial platforms: from dynamic data visualizations to modernized legacy codebases.

Before code, I studied Physics at the University of São Paulo, where I discovered programming through Python and C. After an intensive full stack bootcamp at Driven, I made the web my craft: fast, accessible interfaces with obsessive attention to detail.

Core stack
  • React
  • Next.js
  • TypeScript
  • JavaScript
  • Vite
  • Node.js
  • Python
  • PostgreSQL
  • MongoDB
  • Redis
  • Prisma
  • Jest
  • Docker
  • CI/CD
  • GSAP

Projects.

01 / 03

CapriX IA

Smart farm-management SaaS for goat and sheep herding. By text or voice, farmers talk to Zé, an AI assistant that logs the herd in natural language, answers with science-backed sources (RAG) and raises proactive alerts. In production with farmers in Brazil's semi-arid northeast.

  • Python
  • FastAPI
  • OpenAI
  • Supabase
  • Next.js
02 / 03

News Portal

Most recent freelance: a news website, from responsive layout to article publishing, with a focus on performance and SEO.

  • React
  • SEO
  • Performance
View project
03 / 03

Landing Page for a Medical Clinic

Freelance focused on bringing in patients for new appointments: built the landing page, optimized it for search (SEO) and tracked traffic and conversions with Google Analytics to guide improvements.

  • SEO
  • Google Analytics

Experience.

  1. 2025

    Frontend Developer (freelance)

    Clientes diversos

    Remote freelance work in Brazil: responsive landing pages and web apps for small businesses and medical clinics, with SEO, Google Analytics and end-to-end delivery, from business requirement to shipped interface.

  2. 2024 — 2025

    Frontend Developer

    Quantumz / VeloxQ

    Remote freelance for a Warsaw-based startup (Poland) with a product in production: evolving a legacy React + TypeScript codebase, processing 100k×100k binary matrices with streams and Web Workers, and replacing polling with WebSockets for real-time notifications, owning problems through to delivery.

  3. 2023 — 2024

    Full Stack Developer

    Matmatch (KIT)

    Remote freelance (Germany) on scientific and industrial platforms with a React frontend focus: complex diagrams and dynamic data visualizations, backend contributions in Python and Next.js, and building the frontend of ScienceAI Chat, an AI-for-science platform used at KIT (Karlsruhe).

  4. 2021 — 2022

    Full Stack Bootcamp

    Driven Education

    Intensive full-time web development bootcamp with a hands-on focus on frontend, backend and full stack applications: JavaScript, React, Node.js and both relational and non-relational databases.