Website: https://www.bailleul.dev 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