Freelancer profile translated to English.
Back to original languageAbout Sébastien
Is your codebase getting out of hand? Uncontrolled AI code (Vibe coding/MVP), legacy code that's become untouchable, or technical debt slowing down every delivery.
I transform these codebases into solid foundations, maintainable and mastered by your team.
Senior Fullstack JS/TS with over 10 years of experience on complex B2B platforms, I specialize in two critical situations:
1. AI Project Rescue: From Generated Code to Mastered Code:
Is your AI code (Claude / Copilot / Cursor) difficult to maintain, evolve, or deploy with confidence?
I audit, restructure, and industrialize your code to make it maintainable, testable, and scalable.
2. Legacy Code Refactoring & Migration:
Migrating from Vue 2 to Vue 3, migrating monolithic Node.js to microservices, resolving accumulated technical debt.
I've led these initiatives at Kuzzle (IoT platform with +300k users) and Laëtis (Web Agency), with measurable results: 2x more responsive interfaces, 2x faster builds, -30% development time.
What you get concretely:
- Code Audit: Identification of risks and technical debt, with a prioritized action plan
- Debt Reduction: Targeted refactoring, regained maintainability, facilitated evolutions
- Restructured JS/TS Architecture: Testable, documented, and scalable code without friction
- Reliable CI/CD Pipeline: Linting, strict TypeScript, automated builds, for confident deliveries
- Skill Transfer: Your team gains autonomy and velocity on the delivered codebase
👉 Have a critical project or a codebase to stabilize? Let's discuss it live during an initial call to assess your challenges.
French
Native or bilingual
English
Fluent
Can work on-site
Toulouse (up to 50km), Paris (up to 50km), Bordeaux (up to 50km), Lyon (up to 50km), Montpellier (up to 50km)
Experience
- KuzzleTech Lead Fullstack JS/TS - Refactoring & IoT ArchitectureINTERNET OF THINGS (IOT)September 2022 - February 2025 (2 years and 5 months)Toulouse, FranceTechnical lead on the core product of a large-scale B2B IoT platform (+2M connected objects, 300k users). Mission focused on resolving technical debt, optimizing performance, and mentoring the team.
Achievements & Impact:
- Legacy Frontend Refactoring: Led the overhaul of a Vue 2 application to Vue 3, reducing technical debt and making the interface 2x more responsive.
- Backend Node.js/TS Architecture: Designed complex plugins to enhance multi-tenant isolation on Elasticsearch, ensuring data flow reliability.
- Industrialization: Standardized CI/CD pipelines (linting, TS checks) and optimized them for a 2x reduction in startup and build times.
- Mentoring: Provided technical guidance to 3-4 developers (strict code reviews, skill development in TypeScript and Vue.js).
- AI Tooling: Integrated LLM development assistants to accelerate feature delivery.
🛠 Stack: Vue.js (2 & 3) · Node.js · TypeScript · Elasticsearch · Docker · CI/CD - OpenStudioFull-Stack & DevOps R&D Developer — Microservices ArchitectureSOFTWARE PUBLISHINGMarch 2021 - August 2022 (1 year and 5 months)Toulouse, FranceDesign and development of a high-traffic public service application (+10k daily visitors) within a 10-person team. Mission focused on architectural resilience, modularity, and security of a distributed ecosystem.
Achievements & Impact:
- Microservices Architecture (Event-Driven): Designed an asynchronous synchronization system via MQTT between backend microservices, ensuring data consistency and platform resilience.
- Micro Front-end React: Implemented a modular architecture based on React and Next.js, enabling separation of functional domains for distinct teams.
- R&D DevOps & Security: Proof of concept (POC) and implementation of a secure infrastructure including unified SSO authentication (Keycloak) and distributed object storage (MinIO / S3 compatible).
- Backend & Data: Participated in the development of backend services (PHP/Symfony 6) connected to optimized relational databases (PostgreSQL).
🛠 Stack: React · Next.js · Microservices Architecture · MQTT (Asynchronous) · PHP/Symfony 6 · PostgreSQL · Keycloak (SSO) · MinIO (S3) - ffly4uFullstack JS/TS Developer — IoT Platform & Node/Vue ArchitectureINTERNET OF THINGS (IOT)November 2019 - February 2021 (1 year and 3 months)Toulouse, FranceEvolution and modernization of a B2B IoT platform managing thousands of industrial connected objects, in a context of high real-time data volume and legacy backend.
Achievements & Impact:
- Frontend & No-code Approach (Vue.js): Designed a module allowing clients to visualize and filter data autonomously. Result: 60% reduction in custom development requests.
- Microservices Architecture (NestJS): Created a data export microservice from scratch in TypeScript. Result: reliable process, reduced load on the main backend, and tripled export capacity.
- Data & IoT Optimization: Improved asynchronous processing of IoT trajectories (Node.js / Kuzzle / Elasticsearch) to ensure geolocation data flow consistency.
- DevOps & Cloud (Docker/AWS): Overhauled continuous integration workflows. Result: 2x reduction in image size and build time, accelerating production deployment.
🛠 Stack: Vue.js · TypeScript · Node.js · NestJS · Elasticsearch · Docker · AWS · Kuzzle
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Education
- Certification Machine Learning & Data (RNCP Level 6)OpenClassrooms2025Formation certifiante (Bloc de compétences RNCP 37837) permettant d'allier mon expertise en ingénierie logicielle (10 ans) aux enjeux de la Data et de l'IA. Compétences validées : - Data Engineering & Analyse : Préparation, nettoyage (preprocessing) et exploration des données (EDA) avec Python (Pandas, NumPy). - Machine Learning : Entraînement, optimisation et évaluation de modèles prédictifs (supervisés et non supervisés). - Data-driven Design : Visualisation des tendances (Matplotlib) et intégration d'une logique "donnée" dans la conception architecturale. Cette certification consolide ma capacité à intervenir sur des architectures hybrides (Web + Data) et à auditer avec pertinence des projets liés à l'IA.