About Guillaume
Looking for a Go / Golang developer?
You're in the right place.
I am a software engineer with over 15 years of experience, specialized in Go.
I have collaborated with large companies (Auchan, Chronodrive, Malakoff Humanis) and startups abroad.
I am passionate about software development and, in my free time, I created SignalWhisperBot.
It’s a solution that transcribes voice messages on Signal to save time.
I can support you with:
- Design, development, and maintenance of Go / Golang backends
- Microservices architecture and distributed solutions, containerized with Docker and orchestrated with Kubernetes
- Technical and functional refactoring of existing applications to improve quality, maintainability, and performance
- API development (REST, gRPC)
- Integration with distributed systems (NATS) and databases/caches (PostgreSQL, MongoDB, Redis)
- Deployment automation and CI/CD (GitHub / GitLab)
- Performance optimization, scalability, and application security
- Migration of monoliths to modern architectures
- Monitoring, tracing, and system observability
- Code reviews, documentation, and clean code best practices
- Unit and integration testing to ensure quality and robustness
- Mentoring and technical guidance for less experienced developers
I am autonomous, productive, and results-driven.
My work has been recognized by colleagues for its quality and efficiency, including projects on complex, high-performance, and distributed systems.
Got a project?
Contact me—I respond within an hour.
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Golang developer, Go developer, Go backend developer, backend Golang developer, back-end Go developer, Go software engineer, backend Golang software engineer, Go backend engineer, Golang web developer
French
Native or bilingual
English
Fluent
Can work on-site
Berlin (up to 50km), Munich (up to 50km), Frankfurt am Main (up to 50km), Hamburg (up to 50km), Stuttgart (up to 50km)
Experience
- MEDIAKEYSGolang / Go Backend DeveloperPRESS AND MEDIAAugust 2019 - Today (6 years and 10 months)Paris, FranceMediakeys is an international advertising company founded in 1993, specializing in creating optimized global campaigns. It has over 500 clients in more than 100 countries and 220 experts across 18 offices.I joined the development team of the Arago platform, which enables advertisers to plan, launch, and optimize their online advertising campaigns. The team of 7 to 15 developers worked in Agile.I contributed to the design and development of high-performance backend services, as well as to migrating the platform to a SaaS model based on a more modular and scalable Go microservices architecture.My responsibilities:- Extracting the reporting functionality from a Java monolith into a Go/Golang microservice (gRPC + gRPC-Gateway), implementing 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 enhance observability and service monitoring.- Performing message queue benchmarks to assess performance, scalability, and reliability.- Reviewing merge requests and writing unit and integration tests to ensure code robustness.- Analyzing and redesigning backend APIs to improve performance and maintainability.- Pair programming and mentoring junior developers.Key achievements:- Increased test coverage to over 90%.- Reduced latency of critical calls from several seconds to under one second.- Improved 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, AWS, Prometheus, Grafana, Backend Development.
- SignalWhisperBotGolang / Go Backend DeveloperDIGITAL AND ITJuly 2024 - Today (1 year and 11 months)SignalWhisperBot is an AI-based SaaS product that automatically transcribes Signal voice messages into text to improve productivity and accessibility.I developed this project in my free time to enhance my technical skills in Go.The goal of the project was to provide a privacy-focused transcription service, fully integrated with the Signal app.My responsibilities:- Full design and development of the backend in Go / Golang, focusing on performance, reliability, and low latency.- Creation of a responsive web interface using React.js and Tailwind CSS for a smooth user experience.- Deployment of the infrastructure on Hetzner Cloud using k3d (lightweight Kubernetes) for cost-effective orchestration.- Integration of Stripe for secure subscription and payment management.- Implementation of error tracking with Sentry.- Management of product launch, marketing, and user onboarding workflows.Key achievements:- Delivered a fully functional SaaS in production, from design to launch.- Established a stable architecture capable of handling real traffic with good performance.- Acquired the first users organically through marketing and SEO optimization.Technical context:Go / Golang, MongoDB, React.js, Tailwind CSS, PostgreSQL, Kubernetes, k3d, Docker, GitHub, Hetzner, Stripe, Sentry, Loops, Amazon SES, Backend Development.
- TradeItSenior Backend Developer (Groovy | Grails | Java) and Mobile Developer (Kotlin | Swift)BANKING AND INSURANCEFebruary 2016 - August 2019 (3 years and 6 months)New York, United StatesTrade It is a New York-based startup that allows developers to easily integrate, via an API and SDKs, services enabling their users to connect brokerage accounts, place stock orders, and view their portfolios, orders, and transactions.As the 4th engineer on a dynamic team (4 to 10 developers), I contributed to several key initiatives.My responsibilities:- Led multiple backend developments (Groovy, Grails) on our API that fundamentally impacted our core product, improving system reliability and reducing downtime.- Implemented continuous integration (Jenkins) and wrote unit (Spock) and integration tests, improving test coverage.- Was a primary contributor to the development of our SDKs for iOS (Swift) and Android (Java, Kotlin). (https://github.com/tradingticket/TradeItIosTicketSDK2) (https://github.com/tradingticket/AndroidSDK) (https://github.com/tradingticket/JavaApi)- Worked on innovative projects, such as developing an Alexa "Skill" for voice control on Amazon Echo devices.- Optimized developer efficiency by creating scripts to auto-generate classes needed for integrating a new broker, and by implementing tools like Metabase, allowing non-technical users to query metrics without developer assistance.Technical environment: Groovy, Java, Swift, Kotlin, Grails, Android, iOS, GIT, Spock, Mockito, Quick, Jenkins, GitHub, Alexa, Echo, IntelliJ, Xcode, MySQL, Redis, Backend Development.
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Education
- EngineeringISEN2008ISEN is a prestigious engineering school specializing in training engineers in the digital field since 1956. It is recognized as a Private Higher Education Institution of General Interest (EESPIG), accredited by the CTI, and is a member of CGE, Fésic, and a founding member of Yncréa. I completed the Information Systems and Software Engineering program. Skills: Engineering, Object-Oriented Programming (OOP), Programming, Backend Development, Web Backend Development, Software Engineering, Information Systems, Golang.
- Blockchain & Smart Contract DevelopmentAlyra l'école Blockchain2022Program: - Understanding how blockchains work - Ethereum blockchain and its ecosystem - Solidity development - Solidity smart contracts: best practices and security - Dapp development with Truffle / Hardhat - Continuous integration and delivery - Decentralized finance (DeFi) - NFTs Technical environment: Solidity, Smart Contracts, Ethereum, TypeScript, Next.js, Hardhat, DeFi
Certifications
- Blockchain DeveloperAlyra l'école blockchain2022
- Solana DeveloperAlyra l'école blockchain2025