Freelancer profile translated to English.
Back to original languageAbout Guillaume
Are you looking for a Go / Golang backend developer?
You've come to the right place.
I am a backend developer with over 15 years of experience specializing in Go.
I have collaborated with large companies (Auchan, Chronodrive, Malakoff Humanis) and startups abroad.
I am a person passionate about IT, in my free time, I developed SignalWhisperBot.
It's an AI solution that transcribes voice messages on Signal to save time.
I can assist you with:
- Design, development, and maintenance of Go / Golang backends
- Microservices architecture and distributed, containerized solutions orchestrated with Kubernetes
- Technical and functional redesign of existing applications to improve quality, maintainability, and performance
- API development (REST, gRPC)
- Integration with distributed systems (NATS) and databases/caches (PostgreSQL, MongoDB, Redis)
- Performance optimization, scalability, and application security
- Deployment automation and CI/CD (GitHub / GitLab)
- Migration of monoliths to modern architectures
- Monitoring, tracing, and observability of systems
- Code review, documentation, and best practices for clean code
- Unit and integration testing to ensure quality and robustness
- Mentoring and technical support for less experienced developers
I am autonomous, productive, and results-oriented.
My work has been recognized by my colleagues for its quality and efficiency.
This includes projects on complex, high-performance, and distributed systems.
Do you have a project?
Contact me, I respond in less than an hour.
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Golang developer, Go developer, Go backend developer, Golang backend developer, backend developer, Go back-end developer, Go software engineer, Golang backend software engineer, Go engineer, Golang web developer, Golang developer.
English
Fluent
French
Native or bilingual
Can work on-site
Paris (up to 50km), Bordeaux (up to 50km), Lyon (up to 50km), Lille (up to 50km), Nantes (up to 50km)
Experience
- MediakeysGolang / Go Backend DeveloperPRESS AND MEDIAAugust 2019 - Today (7 years)Mediakeys 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 for the Arago platform, allowing advertisers to plan, launch, and optimize their online advertising campaigns.The team of 7 to 15 developers worked 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 Go microservices architecture, which is more modular and scalable.My responsibilities:- Extraction of the reporting functionality from a Java monolith to a Go / Golang microservice (gRPC + gRPC-Gateway), with the implementation of benchmarks to ensure optimal performance.- Creation of multiple interconnected Go microservices as part of the migration to a microservices architecture and a SaaS model.- Addition of Prometheus metrics to enhance service observability and monitoring.- Benchmarking of message queues to evaluate their performance, scalability, and reliability.- Review of merge requests, writing of unit and integration tests to ensure code robustness.- Analysis and redesign of backend APIs to improve their performance and maintainability.- Pair programming and mentoring of junior developers.I contributed to the following evolutions:- Bringing test coverage to over 90%.- Reducing the latency of certain critical calls from several seconds to less than a second.- Improving the overall reliability and performance of key microservices.Technical context: Go / Golang, gRPC, Protocol Buffers, NATS, Java, Kotlin, Elasticsearch, Meilisearch, Keycloak, PostgreSQL, MongoDB, Redis, Dragonfly, Clickhouse, Kubernetes, Docker, AWS, Prometheus, Grafana, Backend development.
- SignalWhisperBotGolang / Go Backend DeveloperSOCIAL NETWORKSJuly 2024 - Today (2 years and 1 month)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 project's objective was to provide a privacy-respecting transcription service, directly integrated with the Signal application.My responsibilities:- Design and complete development of the backend in Go / Golang, with a focus on performance, reliability, and low latency.- Creation of a responsive web interface with React.js and Tailwind CSS for a smooth user experience.- Deployment of the infrastructure on Hetzner Cloud with k3d (lightweight Kubernetes) for low-cost orchestration.- Integration of Stripe for secure subscription and payment management.- Implementation of error tracking with Sentry.- Management of the product launch, marketing, and user onboarding workflows.Key achievements:- Delivery of a fully functional SaaS in production, from design to launch.- Implementation of a stable architecture capable of handling real traffic with good performance.- Acquisition of 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 (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 services via an API and SDKs, enabling their users to connect their investment accounts, place stock orders, and view their portfolios, orders, and transactions.As the 4th engineer in a dynamic team (4 to 10 developers), I contributed to several key initiatives.My responsibilities:- I led several backend developments (groovy, grails) on our API that fundamentally impacted our core product, improving system reliability and reducing downtime.- I implemented continuous integration (Jenkins) and wrote unit (Spock) / integration tests, improving test coverage.- I was one of the main contributors to the development of our SDKs on iOS (Swift) and Android (java, kotlin). (https://github.com/tradingticket/TradeItIosTicketSDK2) (https://github.com/tradingticket/AndroidSDK) (https://github.com/tradingticket/JavaApi)- I worked on innovative projects, such as the development of a "Skill" for Echo, Amazon's voice control system.- I worked to optimize developer time by creating scripts to auto-generate necessary classes for integrating a new broker or by implementing tools like Metabase, allowing non-technical users to search for 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.
Reviews
Jérôme
EOGILE
Reviewed on 7/31/2019
The whole team enjoys working with Guillaume.
Recommendations
FU
FU
+3
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Education
- EngineerISEN Lille2008L’ISEN est une grande école d'ingénieur spécialisée dans la formation d'ingénieurs dans le domaine du numérique depuis 1956. Elle est reconnu comme étant un Etablissement d’Enseignement Supérieur Privé reconnu d’Intérêt Général (EESPIG). Disposant de l’habilitation de la CTI, membre de la CGE, de la Fésic et membre fondateur d’Yncréa. J'ai suivi le cursus systèmes d'information et ingénierie logicielle. Compétences : Engineering, Programmation orientée objet (POO), Programmation, Développement backend, Développement web backend, Ingénieur logicielle, Information Systems
- Blockchain & Smart Contracts DevelopmentAlyra2022Programme: - Compréhension du fonctionnement des blockchains - La blockchain Ethereum et son environnement - Développement solidity - Smart contract Solidity : bonnes pratiques et sécurité - Dapp et Truffle / Hardhat - Intégration et livraison continues - Finance décentralisée - NFT Contexte technique : Solidity, Smart Contracts, Ethereum, Typecript, Next.js, Hardhat, DeFi
Certifications
- BLOCKCHAIN DEVELOPERAlyra the blockchain school2022
- Solana DeveloperAlyra the blockchain school2025