Website: https://www.bailleul.dev

Guillaume Bailleul

Senior Full-Stack Software Engineer — Go/Python, React, and Distributed Systems

Lille, France · +33 7 81 79 29 34 · guillaume.bailleul@gmail.com · LinkedIn · GitHub

Professional Summary

Senior full-stack software engineer with 15 years of experience designing and shipping complete products: Go and Python backends, APIs, and distributed systems on the server side, React / React Native applications on the client side. I work on critical business integrations and the modernization of existing systems, from architecture through delivery.

Professional Experience

Andjaro / Silae | Senior Software Developer | 2021 - 2026

- Designed a Python/FastAPI LangGraph workflow for payroll-item explanations: 80% less backlog for this category of support requests
- Modernized critical Symfony components, designed payroll / ERP / HRIS integrations, and improved the reliability of AI-assisted development; supported six colleagues in its adoption
- Developed core Elixir/Phoenix platform features and React workflows for the French Ministry of Education

Technologies: Python, FastAPI, Go (R&D), Elixir/Phoenix, React, PostgreSQL, Kafka, Docker, Kubernetes, LangGraph, MCP

Independent (Pagily) | Technical direction and delivery | 2019 - 2021

- Led the architecture and delivery of a document-management platform, from backend services to web and mobile applications
- .NET/C# services, React/Next.js, React Native, and integrations with multifunction printers and scanning equipment

Shipfix (Veson Nautical) | Software Developer | 2019

- Delivered end-to-end product features and a Python/FastAPI API for email parsing and data extraction

Agence Dernier Cri | Senior Software Developer | 2016 - 2019

- Architected and implemented Mailjet SendAPI v3.1 in Go, a distributed API handling millions of requests, delivered on existing GCP infrastructure
- Real-time and data platforms for Leroy Merlin and ADEO: high-frequency ingestion, inter-business-unit authorization, and strategic MVP delivered on schedule

Elicity/Xee | Software Developer | 2013 - 2016

- Designed an IFTTT-like event automation engine and high-traffic distributed IoT platform with RabbitMQ
- Progressively extracted Go, Python, and Node.js services from the Symfony 2 monolith; migrated MySQL to Cassandra and MongoDB

EDF | Software Developer | 2011 - 2013

- Designed a contact-center performance monitoring tool, first deployed regionally and later rolled out nationwide

Education

- Master's degree in Computer Engineering — EFFICOM Lille | 2013
- Professional Bachelor's degree in Industrial Computing and Networks — IUT A de Lille | 2011

Technical Skills

Go, Python/FastAPI, Elixir/Phoenix, TypeScript/Node.js, React, Next.js, React Native, PostgreSQL, Cassandra, MongoDB, Kafka, RabbitMQ, GCP, Docker, Kubernetes, CI/CD, LangGraph, and MCP.

Languages

- French: Native
- English: Professional working proficiency — used both verbally and in writing within international and distributed teams
- Remote collaboration with English, Spanish, Ukrainian, and Russian colleagues