Guillaume Bailleul
Senior Software Engineer
Professional Summary
Senior full-stack engineer and software architect with 12+ years of experience designing and delivering robust systems in production. Specialized in distributed systems, API platforms, modernization programs, and business-critical integrations. Track record of shipping high-impact products from early-stage to scale, while balancing long-term architecture with rapid execution.
Deep expertise in Elixir/Phoenix, technology-agnostic decision-making, and strong ownership from design to delivery.
Professional Experience
Senior Software Developer
Andjaro | Paris, Ile-de-France, France (Remote, English)
October 2021 - Present
Andjaro is a workforce management platform serving healthcare, public sector, retail, and facility management organizations.
- Architected and built core HR backend capabilities in Elixir/Phoenix
- Maintained and modernized Symfony legacy systems while preserving production stability
- Co-architected mobile workflows with React and Clojurescript integration
- Designed integration interfaces with payroll, ERP, planning, and SIRH ecosystems
- Collaborated across a multinational engineering team in remote-first delivery
Technologies: Elixir, Phoenix, React, Clojurescript, Symfony2, PostgreSQL, Docker
Freelance Software Engineer
Independent (Pagily) | Lille Region, France
December 2019 - October 2021
Pagily is a document management platform focused on paperless workflows, universal scanning, and secure printing.
- Led technical direction and architecture decisions for the product
- Built backend services in .NET/C# for secure document processing and indexing
- Developed frontend application in React and mobile app in React Native
- Implemented OCR/ML-driven document classification and indexing pipelines
- Designed integrations with multifunction printers and scanning devices
Technologies: .NET, C#, React, React Native, PostgreSQL, OCR/ML
Software Developer
Shipfix (Veson Nautical) | Paris, Ile-de-France, France (Remote, English)
April 2019 - November 2019
Shipfix is an AI-enabled platform for maritime chartering and operations.
- Developed backend services in Python and Elixir for real-time processing
- Built ML-powered email parsing and data extraction features
- Implemented interactive workflows in Vue.js for opportunity matching
- Contributed to collaboration tools and real-time analytics features
Technologies: Python, Elixir, Vue.js, ML/AI, PostgreSQL, Docker
Senior Software Developer
Agence Dernier Cri | Lille Region, France (Remote, English)
August 2016 - April 2019
Mailjet SendAPI v3.1
- Architected and implemented Mailjet SendAPI v3.1 in Go
- Delivered distributed architecture capable of handling millions of email requests
- Integrated Cassandra message storage with legacy Freepascal systems
Leroy Merlin Monitoring Platform
- Built real-time monitoring system with Elixir/Phoenix backend and React Native app
- Designed high-frequency data ingestion pipelines across business units
Consulting Contributions
- Cityscoot: architected scalable APIs for high-traffic mobility workloads
- Les Hotels tres particuliers: stabilized legacy systems, reduced technical debt, and enabled team handover
Technologies: Elixir, Phoenix, React, React Native, TypeScript, Go, Cassandra, PostgreSQL
Software Developer
Elicity | Lille, France
December 2013 - July 2016
- Core engineer on a high-traffic IoT platform serving thousands of connected devices
- Designed an event automation system similar to IFTTT
- Led migration from MySQL to Cassandra and MongoDB
- Drove monolith-to-microservices transformation from Symfony2
- Migrated persistence layer to a high-performance Go REST API
- Built distributed ingestion platform with Java and RabbitMQ
- Implemented CI/CD and deployment tooling with Docker, Jenkins, and Ansible
Technologies: Java, Go, Node.js, PHP (Symfony2), RabbitMQ, Cassandra, MongoDB, MySQL, Docker, Jenkins, Ansible, Python
Technical Skills
Languages: Elixir, TypeScript, Go, C#, PHP, Python, Clojure, Clojurescript, .NET
Frontend: React, React Native, Next.js, CSS/SCSS
Backend: Elixir/Phoenix, Go, Node.js, Symfony2, Java, Clojure
Queueing: RabbitMQ, Redpanda (Kafka)
Databases: PostgreSQL, MongoDB, Cassandra, MySQL
DevOps & Infrastructure: Docker, Kubernetes, Jenkins, Ansible, AWS, GCP
Specializations: System Architecture, Microservices, Distributed Systems, IoT Platforms, API Design, Full-Stack Development
Key Achievements
- Architected systems processing millions of events/operations across distributed infrastructure
- Implemented Mailjet SendAPI v3.1 as a foundational high-scale API
- Led monolith modernization and migration programs toward microservices
- Drove complex multi-database migration strategies across production systems
- Mentored engineers and established architectural best practices
Languages
- French: Native
- English: Professional working proficiency