Lenny Garnier

Full Stack Engineer

Créteil, Île-de-France, France6 yrs 3 mos experience

AI EnabledAI ML Practitioner

Key Highlights

Expert in building reliable AI-powered applications.
Proven track record in secure financial systems development.
Strong experience in full-stack development with modern frameworks.

Stackforce AI infers this person is a Fullstack Software Engineer with expertise in Fintech and AI-driven applications.

Contact

Skills

Core Skills

Node.jsTypescriptNestjsReactReact Native

Other Skills

Large Language Models (LLM)React.jsFrançaisDockerPostgreSQLTanStack TableDéveloppement agileInterface de programmation d’application (API)JSONGitHubBashRevue de codeGitDevOpsPrisma ORM

About

Fullstack Software Engineer with 3 years of experience building TypeScript-based systems with NestJS and React. I specialize in reliable backend architectures, API design, and AI-powered applications, focusing on data integrity and production-ready systems. Currently building MonAmiChef, an AI cooking assistant that generates personalized recipes using structured JSON outputs and Zod schema validation to reduce LLM hallucinations in production. Previously worked at Polycea on secure financial systems (gold trading vault, Hexagonal Architecture, Core Banking API integration) and at Racemappr on a full React Native / Node.js product. Stack: TypeScript · NestJS · React · React Native · PostgreSQL · Prisma · Docker Open to Fullstack opportunities — Paris or Remote.

Experience

6 yrs 3 mos

Total Experience

4 yrs 3 mos

Average Tenure

Current Experience

Witik

Full Stack Engineer

Apr 2026 – Present · 1 mo · Paris · On-site

Node.jsTypeScriptLarge Language Models (LLM)React.js

Polycea (ex polyconseil)

Développeur Full Stack

May 2025 – Jan 2026 · 8 mos · Paris · Hybrid

Worked as a Fullstack Engineer on high-impact digital products involving secure financial data and complex backend systems.
Designed a centralized data synchronization system using Hexagonal Architecture to ensure real-time consistency across applications
Developed a secure “Vault” module for gold trading, integrating the Skaleet Core Banking platform
Built reusable headless UI components using TanStack Table to standardize data grids across the application
Improved system reliability by refactoring authentication flows and strengthening data integrity checks, reducing production errors by 30%
Tech stack: NestJS, React, TypeScript, PostgreSQL, JWT Authentication, TanStack Table

React.jsTypeScriptFrançaisNestJSDockerPostgreSQL+2

Racemappr

Développeur Full Stack

Sep 2024 – May 2025 · 8 mos · Remote

Worked on both web and mobile applications in a fast-paced development environment, delivering features across the full stack.
Increased sprint velocity by 15% by improving development workflows and code review practices
Built an AI-assisted calendar component to suggest personalized goals and enhance user engagement
Implemented unified authentication across web and mobile platforms using JWT
Developed scalable front-end and back-end features for a public-facing application
Tech stack: React Native, Node.js, Supabase, Prisma, TypeScript

Développement agileDevOpsPrisma ORMGitLabReact.jsTypeScript+17

Feelbat

Développeur Full Stack

Apr 2023 – Aug 2023 · 4 mos · Saint-Denis · On-site

Contributed to the development of a mobile application connected to IoT crack detection sensors.
Improved application loading performance by 40% compared to the original MVP
Led the transition from MVP architecture to a more scalable and maintainable system
Implemented Bluetooth pairing between the mobile application and hardware sensors
Led front-end development efforts, focusing on reusable components and long-term maintainability
Tech stack: React Native, TypeScript, Bluetooth integration

TypeScriptScrumReact NativeFrançaisContinuous Integration and Continuous Delivery (CI/CD)Interface de programmation d’application (API)+3

Phar (réunion)

Epitech Innovative Project - Lead Mobile Engineer

Nov 2022 – Feb 2025 · 2 yrs 3 mos · Reunion · Remote

Led the mobile development of PHAR, a music discovery application that generates playlists based on user mood and listening preferences.
Designed and developed the mobile application using React Native and TypeScript
Implemented the core playlist generation logic and recommendation features
Collaborated with a multidisciplinary team in an agile environment
Contributed to product design and feature planning from early prototype to working MVP
Tech stack: React Native, TypeScript, Agile development

Développement agileReact.jsTypeScriptReact NativeGitHubFrançais+3

Epitech

2 roles

Pedagogical Assistant

Oct 2022 – Mar 2023 · 5 mos

Worked on an existing production codebase to deliver new features and maintain system stability.
Developed new features across the application stack
Investigated and fixed recurring bugs to improve reliability
Collaborated with the engineering team to maintain code quality and consistency

GitHubFrançaisBashJSONRevue de codeGit

Student

Sep 2019 – Dec 2025 · 6 yrs 3 mos

Développement agileFrançaisInterface de programmation d’application (API)JSON

Solarplexus s.a.s

Software Engineer

Aug 2021 – Dec 2021 · 4 mos · Saint-Benoît · On-site

Worked on maintaining and improving an existing web application within a production codebase.
Investigated and resolved recurring bugs across the application stack
Contributed to improving system stability and application reliability
Collaborated with the engineering team to understand and navigate a legacy codebase
Assisted in implementing minor features and improving existing components
Tech stack: PHP, SQL, HTML, JSON

ScrumFrançaisJSON