Guillaume Debavelaere

SignalWhisperBot is an AI SaaS product that automatically transcribes Signal voice messages into text to improve productivity and accessibility. I founded and built it from scratch as a solopreneur — handling every stage from product design to development, deployment, and marketing. The project’s goal was to provide a privacy-friendly transcription service directly integrated with the Signal messaging app. My responsibilities: - Designed and developed the entire backend in Go / Golang, focused on performance, reliability, and low latency. - Built a responsive web interface using React.js and Tailwind CSS for seamless user experience. - Deployed the infrastructure on Hetzner Cloud using k3d (lightweight Kubernetes) for low-cost orchestration. - Integrated Stripe for secure billing and subscription management. - Implemented error tracking with Sentry - Managed product launch, marketing, and user onboarding workflows. Key achievements: - Delivered a fully functional SaaS in production, from concept to launch. - Achieved a stable architecture handling real user traffic with strong performance. - Acquired early users organically through marketing and SEO optimization. Technical context: Go / Golang, MongoDB, React.js, Tailwind CSS, PostgreSQL, Kubernetes, k3d, Docker, GitHub, Hetzner, Stripe, Sentry.

Mediakeys is an international advertising company founded in 1993, specializing in creating optimized global campaigns that combine local expertise with international reach. The company serves over 500 clients in more than 100 countries and has 220 experts across 18 offices worldwide. I joined the development team of the Arago platform, which allows advertisers to plan, launch, and optimize their online advertising campaigns. The team (7 to 15 developers) operated in an Agile environment. I contributed to the design and development of high-performance backend services, as well as the migration of the platform to a SaaS model based on a modular and scalable Go microservices architecture. My responsibilities : - Extracting the reporting functionality from a Java monolith into a Go microservice (gRPC + gRPC-Gateway), including benchmarks to ensure optimal performance. - Creating multiple interconnected Go microservices as part of the migration to a microservices architecture and SaaS model. - Adding Prometheus metrics to improve service observability and monitoring. - Conducting message queue benchmarks to evaluate performance, scalability, and reliability. - Reviewing merge requests and writing unit and integration tests to ensure code robustness. - Analyzing and refactoring backend APIs to improve performance and maintainability. - Pair programming and mentoring junior developers. Key contributions : - Increased test coverage to over 90%. - Reduced latency of critical calls from several seconds to under one second. - Improved the overall reliability and performance of key microservices. Technical context : - Go / Golang, gRPC, Protocol Buffers, NATS, Java, Kotlin, Elasticsearch, Keycloak, PostgreSQL, MongoDB, Redis, Clickhouse, Kubernetes, Docker, Git, GitLab, AWS, Prometheus, Grafana, Message Broker, Distributed Systems

TradeIt provides secure trading services, enabling users to trade seamlessly from any app or website using their existing brokerage accounts. As the 4th engineer in a dynamic team (4-10 developers), I contributed to multiple key initiatives, working on-site in New York before transitioning to remote work for the final year. Backend: - Integrated new brokers and implemented core features, ensuring system scalability and reliability. - Refactored the core system to create a framework that accelerated client onboarding and reduced outages. - Improved test coverage and created a scaffolding script to streamline new broker integration. DevOps & Analytics: - Set up continuous integration with Jenkins to streamline deployments. - Implemented Metabase to empower non-technical stakeholders to access metrics independently. iOS Development: - Led the refactor of the TradeIt SDK into the new TradeIt SDK 2 using Swift, introducing order and transaction screens. https://github.com/tradingticket/TradeItIosTicketSDK2 Android Development: - Developed an SDK wrapping a Java API, transitioning to Kotlin for modernized codebases. https://github.com/tradingticket/AndroidSDK https://github.com/tradingticket/JavaApi Voice Assistant Development: - Created an Alexa skill to provide market data and manage stock watchlists, showcasing innovation in voice interface design. Key Achievements: - Improved system reliability and scalability through refactoring and optimizations. - Demonstrated adaptability by mastering multiple technologies, including Kotlin, Swift, RxJava, and more. - Maintained productivity and responsiveness in a remote setup with a 7-hour time difference. Technical environnement : Groovy, Java, Swift, Kotlin, Grails, Android, iOS, GIT, Spock, Mockito, Quick, Jenkins, Github, Alexa, Echo, IntelliJ, Xcode, MySql, Redis.

Creation of a platform that connects people who need their racket restrung with those who own a stringing machine. Technical environment: MEAN stack (MongoDB, Express.js, Angular.js, Node.js), GIT, Asana, Testlink

Development of an environmental monitoring webapp from scratch for the New-Caledonian startup DORA, which displays data collected by underwater probes disseminated in the New-Caledonian lagoon. Use of Spring Boot making it easy to create stand-alone, production-grade Spring based Applications that you can "just run". Technical environnement : Java/J2EE, Spring boot, Spring MVC, Spring data-jpa, Spring Security, Thymeleaf, Maven, GIT, Tomcat, IntelliJ, jQuery, Hibernate, Postgresql, Linux, Openshift.

Humanis is a group of accident insurance, health, pension, employing over 6000 people. Department of retirement applications and customer relations Software components maintener (Designer – Developer profil) – Java / SOA Perimeter, in a team of 5 developers. - CRM and payroll management applications development and maintenance - CRM inbound email queue optimisation : migration to a JMS queue, integration with the Eptica multi-channel solution API via batch scripts. - Creation and Deployment of an archiving solution for yearly salary declaration. Integration with the Alfresco EDM solution via the CMIS protocol. Technical environnement: Java/J2EE, Spring MVC, jQuery, Hibernate, Junit, Unitils, Maven, Eclipse, Netbeans , SVN, Hudson, Sonar, OpenESB, Alfresco, ActiveMQ, MongoDB, Tomcat, Jboss, AppDynamics, Redmine, Mantis, Eptica.

Chronodrive.fr (Business Unit Retail & Industry, E-commerce Team) - Led migration and internationalization of the Chronodrive.fr website, focusing on process automation. Auchan.fr (Business Unit Retail & Industry, E-commerce Team with 10–25 coworkers) - Software Evolution Development: Enhanced Auchan.fr website functionality, managing technical and functional specifications, budgeting, technical analysis, design, testing, benchmarking, and delivery. - Key feature development: Integrated search engine via web services, developed administration tools for product ranking, and prepared seasonal sales. - Front-End Overhaul: Led a major front-end rework, leveraging Spring and Tapestry; implemented layers to separate front-end from core systems, used mocking objects, unit testing, and Hudson for continuous integration. - Application Maintenance: Provided maintenance for third-party applications, correcting defects and implementing enhancements. Technical environnement: Java/J2EE, Eclipse, Spring, Tapestry, Javascript, Jquery, SolR, Junit, Jsp, Mysql, Hudson, Sonar, Jira, Redmine, Linux, Maven, Tomcat, Json, Webservices

Atos Worldline is the leader and reference player in the field of electronic payment and transactional activities in europe. 7200 employees, 1,1 billion euros turnover, present in 17 countries. Business Unit Retail & Industry, Team Labs - Designed and Developed proof-of-concept projects and led a team of interns. - Developed Rich Client Administration Tools for invoice simulation, coupon management, marketing campaign management (workflow engine), and customer targeting for Supermarchés Match, Intersport, and SFR. - Conducted Code Reviews and created framework documentation and best practices to support new interns and ensure code consistency. - Shell Project: Developed an administration interface for paperless invoicing. Technical Environment: Java/J2EE, Eclipse, Spring, Tapestry, JavaScript, jQuer, JUnit, JSP, MySQL, Hudson, Sonar, Jira, Redmine, Linux, Maven, Tomcat, JSON.