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Guillaume Saint EtienneGS

Guillaume Saint Etienne

Senior Developer / TechLead / Architect / CTO

€650/day
Toulouse, FR
15+ years

Average response time: 1 hour

Freelancer profile translated to English.
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About Guillaume

I am a Solutions Architect, focusing on BackEnd .NET Core, Java/Kotlin, hexagonal architecture, cloud native, entire ecosystem, open source projects, trainer C# + TypeScript + Java + Kotlin, senior expertise DDD, TDD, BDD. Agile mindset. Speaker. Agentic coding since summer 2024.
  • French

    Native or bilingual

  • English

    Fluent

Can work on-site
Toulouse (up to 50km)

Experience

  • GSC Integrations & Consulting
    CEO + CTO / Backend Tech-Lead / .NET Core Solution Architect
    DIGITAL AND IT
    August 2022 - Today (3 years and 10 months)
    Experienced in building enterprise‑grade platforms from scratch using .NET Core, C#, TypeScript or Java, and modern cloud/open‑sourced stacks. Led a 30‑month mission at ITER.org, designing the core of ICP4 (Integrated Content Platform), gathering large‑scale engineering and business data. Strong expertise in Hexagonal Architecture, scalable REST APIs, Docker, MongoDB, event‑driven systems, DDD/TDD, and CI/CD. Agentic Coding with Claude since 2024. Also led teams delivering Azure‑based or self‑hosted APIs, Angular front‑ends, and enterprise telephony systems (Microsoft Teams). Skilled in workflow design, software models, collaborative tooling, DevOps, technical strategy for SMEs & retail environments.
    Microsoft Azure Docker TDD/BDD API RabbitMQ
  • Pools
    SENIOR DEVELOPER
    SOFTWARE PUBLISHING
    January 2022 - July 2022 (6 months)
    Bordeaux, France
    Funding a Domain StoryTelling workshop with POs, UX then dev for a new project (artists worlds). Learning blockchain principles and Event Sourced architecture by JB Dusseaut. Using Kotlin to propose a new implementation of the Java seed on GCP with Vertx. Coding in pair programming using KotlinTypeScriptReact.
  • Primobox
    TECHNICAL LEAD / SENIOR DEVELOPER / DDD ADVISOR
    February 2021 - December 2021 (10 months)
    Helping in the product strategy with DDD insights and workshops counselor for the CTO and the CEO: Business Canvas, Wardley Maps, Event Modeling, Domain Story Telling, Miro, Slack, Jira, Jenkins, Docker. CODE: Kotlin, Java, Spring Boot, JPA, Mongo DB, Artemis. METHODS: DDD, TDD, Mutation Testing, Sonar, Promyze, ArchUnit ... DevOps mindset.

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Education

  • ZX81
    ZX81
  • Universit« PaXO SaEatier

Skill set

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