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Sylvain LeroySL

Sylvain Leroy

Tech Lead Backend Java — Cloud & GenAI Agentic AI

€500/day
Lausanne, CH
15+ years

Average response time: 1 hour

Freelancer profile translated to English.
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About Sylvain

Tech Lead freelance with 15+ years of experience, I help companies modernize their Java backends, succeed in their cloud transition, and integrate GenAI and agentic systems into their products.

What I do:
  • GenAI & Agentic AI — LLM integration (OpenAI, Anthropic, Mistral), RAG, autonomous agents, orchestration (LangChain, LangGraph), MCP, function calling, evaluation & observability
  • Backend Java / Kotlin / Spring Boot — architecture, REST API, microservices
  • Cloud GCP & AWS — legacy migration, cloud-native, Kubernetes, Terraform
  • DevOps & CI/CD — Software Factory, Jenkins, SonarQube, test automation
  • Tech leadership — scoping, architecture reviews, team coaching (10+ devs)

GenAI Use Cases I Cover:
  • • Business chatbots & assistants connected to your data (RAG)
  • • Multi-step autonomous agents (search, decision, action via tools)
  • • Workflow automation via LLM (extraction, classification, summarization)
  • • Secure GenAI integration in enterprise environments
  • Typical results:
  • • Migration of legacy systems to modern cloud architectures
  • • Deployment of secure and observable GenAI assistants
  • • CI/CD pipelines reducing time-to-market
  • • Reduction of technical debt through audits and quality standards
Ideal for:banks, insurance companies, scale-ups, and large enterprises looking to industrialize their first GenAI use cases, or modernize their backend while preparing for the arrival of AI in their products.

Stack:Java • Kotlin • Spring Boot • Python • OpenAI • Anthropic • LangChain • LangGraph • RAG • Vector DBs • GCP • AWS • Kubernetes • Docker • Terraform • Jenkins
  • Based in Lausanne — on-site (up to 100 km) and remote. Bilingual FR / EN
  • English

    Fluent

  • French

    Native or bilingual

  • German

    Basic

Can work on-site
Lausanne (up to 50km), Lausanne (up to 100km)

Experience

  • Association OnlyWine.ch
    Digital Content Assistant
    May 2025 - Today (1 year and 2 months)
    Épalinges, VD, Switzerland
    I am providing non-monetary support for the growth of the OnlyWine.ch association project in Switzerland including digital creation, website management, online shop creation.
  • Amazon Web Services (AWS)
    Specialist Solution Architect - Migration and Application Modernisation
    January 2023 - Today (3 years and 6 months)
    Switzerland
    I'm involved in Cloud Migration from building our customer business case, cost optimization, to POC, Architecture design Workshop and daily support.
  • KEYTEO
    Techlead mission
    April 2021 - August 2021 (4 months)
    Lausanne, VD, Switzerland
    My involvement in a team of approximately 10 people was to build the solution design and technical specifications for the developers and testers. The projet was ordered to deliver REST and asynchronous interfaces, to plug the existing systems to Syrius

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Education

  • Master 2 Research in Computer Science
    Université de Rennes 1
    2007

Skill set

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