Freelancer profile translated to English.

Description

Your B2B SaaS application is functional in MVP, but you're facing performance, stability, or scalability limitations on the back-end?

I step in to design, take over, or evolve back-end APIs and architectures, with a product-oriented approach and a modern stack based on NestJS, Node.js, and TypeScript. The goal: deliver robust, secure, and production-ready solutions.

As a back-end developer specializing in NestJS, I cover the entire server layer: structured REST APIs, secure authentication, data management, and third-party integrations. I build maintainable back-ends, free from technical debt or unnecessary complexity.

I've worked on various projects:

REST APIs forB2B SaaS applications and business platforms

Back-ends withauthentication, roles, multi-tenancy

Third-party service integration:payments (Stripe, PayPal), external APIs, webhooks

Modular architecture for AI assistants:OpenAI orchestration, vectorization, multi-project isolation

Volume management: query optimization, PostgreSQL indexing

Custom CRM with automation and real-time sync

This diversity allows me to quickly understand your business challenges, technical constraints, and long-term objectives.

My approach is turnkey: clear architecture, separation of concerns, secure flow management, documented code designed for evolution.

Tech Stack: **TypeScript, JavaScript, Node.js, NestJS, Express, PostgreSQL, MongoDB, Prisma, TypeORM**, REST API, JWT, OAuth 2.0, automated tests, data validation, application security.

Looking for a back-end developer who can design or strengthen a critical server architecture for your product?

Contact me for an initial discussion. I respond within 1 hour, and we can quickly arrange a video call to scope your project.

Industry field of expertise

Languages

French
Native or bilingual
English
Conversational
Italian
Fluent
German
Basic

Workplace preferences

Can work on-site

Paris (up to 50km), Lyon (up to 50km), Marseille (up to 50km), Bordeaux (up to 50km), Toulouse (up to 50km)

Doss-ia
Fullstack Developer React Node
CIVIL ENGINEERING
November 2025 - Today (9 months)
Paris, France
Context:

In the construction sector, analyzing written documents (CCTP, DPGF, regulations) is a time-consuming task prone to human error. An omission in a technical clause can lead to hundreds of thousands of euros in disputes or additional work.

Solution:
Implementation of a RAG architecture. This engine allows for surgical document analysis, cross-referencing technical data to detect anomalies and contradictions between different lots.
SaaS Multi-Tenant & Quotas Management: Implementation of a robust system for managing companies and users. Real-time monitoring of consumption (scanned pages, messages sent) with strict quota enforcement based on the subscription plan (Essential, Business, Enterprise).
B2B Hybrid Payment Engine:
PayPal Recurring: Full integration of the Subscriptions API for automated monthly billing.
Bank Transfer Flow: Automation of the subscription process via bank transfer with pro-forma invoice generation and manual validation workflows for large accounts.
Infrastructure & Document Processing: High-performance processing pipeline including OCR, semantic chunking, and vector indexing in PostgreSQL (Vector Extension). Ensures ultra-precise context retrieval for AI.

Delivery of a mature and secure SaaS platform capable of processing large market files (over 3000 pages) with immediate responsiveness. DossIA now allows engineers and site managers to significantly reduce document analysis time while increasing the reliability of technical audits.

The platform offers construction companies a 360° view of their contractual commitments, transforming raw data into decision-making intelligence.
Microsoft Azure Artificial Intelligence Next.js NestJs SQL
Beev
Fullstack Developer React / NestJS
AUTOMOBILE
October 2025 - October 2025
Paris, France
Context

Beev, a scale-up specializing in electric mobility solutions (B2B/B2C charging station installation), wanted to migrate its customer portal from a no-code solution to a more robust, modular, and maintainable React / NestJS architecture.

The objective was to regain control over the source code, improve performance, customization, and direct integration with internal tools (HubSpot, internal APIs, etc.).

Solution

Technical Migration: Taking over the existing front-end within an Nx monorepo containing multiple applications (backoffice, SaaS, etc.).
I worked from an existing folder architecture, respecting the shared structure (domain-driven design, separation by domain contexts, features, shared, etc.).

Front-end
Development of the customer portal in React, with React Hook Form, Zod for schema validation, and Zustand for global state management.
Integration of i18n for multilingual interface management.
Redesign of key components in compliance with the Beev design system.

Back-end
Development and integration of APIs in NestJS, with PostgreSQL as the database and Docker for environment management.
Implementation of a system for retrieving customer data from HubSpot (synchronization via REST API).
Verification of transaction integrity and atomicity.

Methodology

Agile collaboration with product and design teams.
Code documentation, standardization of conventions, and use of Husky + lint-staged for commit quality.

Result

The new solution offers a fluid user experience, better internationalization, and a solid technical foundation for future B2B evolutions at Beev.
NestJs Docker React.js Hubspot
Smart Invoice
Full Stack Developer
CONSULTING AND AUDITS
June 2025 - Today (1 year and 2 months)
Paris, France
Context:

A client wanted an intelligent tool for creating and managing quotes/invoices, capable of automating invoice generation and analyzing incoming documents.

Solution:

Development of a quote/invoice editor with automatic generation of associated invoices.
Integration of an OCR engine to analyze imported PDF invoices and automatically extract key data (amounts incl./excl. tax, SIRET, client, payment status).
Implementation of dynamic VAT calculation and real-time payment tracking.
Secure architecture with NestJS, Prisma, PostgreSQL, JWT.
Modern front-end with Next.js + TailwindCSS and test automation (Jest, Cypress).

Result:

A turnkey solution that saves users several hours per week by reducing manual entry and improving payment tracking reliability.
NestJs PostgreSQL Prisma Vercel Typescript

Check out Thomas's experience

Foued

dévelopeur - INFINITY LOGICIELS

Reviewed on 4/1/2026

I had the opportunity to work with Thomas on the design and complete development of our DossIA platform, and his level of involvement and technical expertise were crucial to the project's success. Thomas started from scratch, taking charge of the entire technical architecture: - Back-end and front-end design - Setting up a scalable architecture - Advanced integration of Microsoft Azure services (cloud, OCR, conversational AI, cache management) - Development of a high-performance RAG (Retrieval-Augmented Generation) system for document analysis Beyond his solid technical skills (NestJS, React/Next.js, Prisma, etc.), Thomas demonstrated a real product vision. He didn't just develop; he structured, optimized, and anticipated issues related to performance, scaling, and product evolution. His ability to handle complex subjects like OCR, intelligent document analysis, and AI pipelines is a real asset, all with a pragmatic, results-oriented approach. I recommend Thomas without hesitation for any project requiring a robust, scalable, SaaS-oriented back-end, especially for challenges involving data, AI, and automation.

Mahmood

Numbers Knowhow Limited

Reviewed on 9/22/2025

I have worked with a number of developers over the years and Thomas has proved to be one of the good guys - knowledgeable, professional, effective, puts forward suggestions, and has been a delight to work with. Thomas is leading the project development for Budgetwhizz, our SAAS product, Thomas would be a good addition to any development I have collaborated with many developers over the years, and Thomas has proven to be an excellent collaborator: knowledgeable, professional, effective, always attentive, and a real pleasure to work with. Thomas is leading the development of Budgetwhizz, our SaaS product. He would be a valuable asset to any development project.

Show all 3 reviews