Full-stack developer

ALEXIS

UI/UX designer

LAVIGNE

Rouen, France
/ On the menu

Skills, projects, background

Seven angles on what I do, three flagship projects, the context behind them. All just below.

/ My skills

What I do best

Seven angles on what I do and how I do it.

Solo, full stack

01. I build products, not just code

StreamSync is my personal lab: a solo-built Twitch × Spotify SaaS, with first revenue expected in April 2026. Architecture, frontend, backend, browser extension, Discord bot, Stripe integration: I handled every layer.

  • Next.js + Node.js + Express + Postgres
  • Chrome MV3 + Firefox extensions
  • Spotify Web Playback SDK + Twitch API
  • Stripe + multi-provider OAuth
Same brain

02. Design and code aren't two different people

On Figma, I'm already thinking in React components, Tailwind breakpoints, error states. UI starts from the same place as the architecture, which keeps the mockups grounded in the final product.

  • Figma: design systems, prototypes
  • Typed React components
  • Tailwind: tokens and themes
  • Illustrator, Photoshop when needed
Polyvalent by necessity

03. When an internal tool speaks 4 languages, you learn

At Altitude, I led 3 tools in parallel, each on a different stack: React + Express + SQL Server, Next + Symfony + Postgres, and a React + Express dashboard. No comfort of a single stack.

  • React, Next.js, Vite
  • Node.js, Express
  • PHP Symfony, ASP.NET
  • PostgreSQL, Supabase, SQL Server
Under the hood

04. Minecraft mods (Java), Rust mods (C#)

When the tool doesn't exist, I write it. Minecraft server plugins in Java, Rust client mods in C#. A personal exercise that taught me low-level discipline.

  • Java server plugins
  • C# client mods
  • Tooling and scripting
  • Light reverse engineering
In front of a group

05. React/Express training at CESI, one month

Designed the program, wrote the materials, ran the sessions. In front of a group, clarity is non-negotiable, and you end up understanding what you teach better.

  • Program design
  • Teaching materials
  • Running sessions
  • Individual follow-up
Toronto, Altitude, mixed teams

06. Comfortable when the context shifts

York on an international team, Altitude on a mixed apprentice/full-time team, CESI alone in front of a group. Learning a new context doesn't slow the work down, it's part of it.

  • Operational English, written and spoken
  • Aligning with existing conventions
  • Remote or in-person, no friction
  • Understanding a domain before coding it
The third way

07. StreamSync exists because DMCA blocks options 1 and 2

Re-adding music to a Twitch VOD without breaking DMCA: not server-side, not in the video, but at the viewer. This perspective shift is the foundation of the whole SaaS.

  • DMCA-safe viewer-side architecture
  • Companion Discord bot
  • OAuth Spotify + Twitch + Discord
  • Freemium via Stripe
/ About

Someone who builds

23, full-stack developer and UI/UX designer in Rouen, France. Soon-to-be CS engineer at CESI, entrepreneurship track. I develop internal tools in apprenticeship at Altitude Infra, and StreamSync, a Twitch x Spotify SaaS, in parallel. Plus several other personal projects for experimenting.

LinkedInGitHub
/ Career

Experience

  • Software engineerAltitude Infra, Val-de-Reuil, France2023 - ongoing
  • R&D internshipYork University, Toronto, Canada2025
  • React / Express trainerCESI, Rouen, France2025
  • Self-employedOn the side, Rouen, Francesince 2025
  • Development internshipsSafran Nacelles, Le Havre, France2022 - 2023

I design and I code, solo or in a team. I adapt the stack to the problem, not the other way around. When the tool doesn't exist, I build it. The goal isn't a perfect mockup, it's a product that actually works.

Teamwork, Communication, Organization, Rigor, Creativity.

/ Selected work

A few projects

A sample of my current projects. Some are public, others under NDA.

Currently building

StreamSync

SaaS that lets viewers replay the original music on Twitch VODs, perfectly synced to the live moment. DMCA-safe on the Twitch side.

  • Next.js
  • Node.js
  • Express
  • Stripe
  • Twitch API
  • Spotify API
  • Supabase
View project
Two-person redesign

Drafted

Inclusive Valorant esport platform, a safe space for women and marginalized genders. Complete two-person redesign, from scratch: new visual identity, rethought navigation, refocused player experience.

  • Next.js
  • Tailwind
  • Supabase
  • Prisma
  • Figma
Confidential
Lead dev

Three internal tools

HUB AI, VIGIE and HUB DSI: three internal platforms built in apprenticeship. From the centralized portal to field inventories.

  • React
  • Next.js
  • Express
  • Symfony
  • PostgreSQL
  • SQL Server
Confidential
York University, Toronto, Canada

SmartGSN

Lucidchart-style collaborative platform for Goal Structuring Notation. International mobility internship.

  • React
  • Real-time
  • Academic research
Confidential
/ Off the clock

What runs when the code stops

  • Travel

    Canada, USA, Europe. Travel opens me up to other cultures, other rhythms, other ways of living.

  • Movies

    Movies, to clear my head and find inspiration. Marvel and Star Wars at the top of the list.

  • Music

    Music puts me in my bubble. When Linkin Park is playing, I can code for hours without breaking focus.

  • Video games

    Video games feed my creativity, sharpen my focus, train my sense of team play.

  • Sport

    Going for a run is the break that really resets me in a day spent behind the screen.

/ Contact

Let's work together?

contact@alexis-lavigne.com
LinkedInGitHub