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Xavier JulienXJ

Xavier Julien

Java/Spring/Kafka Developer - VueJs/React

€500/day
Bordeaux, FR
3-7 years

Average response time: 1 hour

Freelancer profile translated to English.
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About Xavier

Hello 👋,

I am a Java Backend Developer with solid Full-Stack experience, particularly in technically demanding environments (Consulting Firms, Large Corporations).
I specialize in Java, Spring Boot, microservices/hexagonal architectures, and event-driven processing (Kafka).

⚙️ Backend

I design and maintain robust, scalable, and secure backend systems:

👉 Java 11 → 21 (Spring Boot 2/3, hexagonal architecture, DDD)
👉 Microservices, secure REST APIs, role & permission management
👉 Apache Kafka / Kafka Connect, event streaming, data pipelines
👉 PostgreSQL, MongoDB, SQL optimization, transactions, migrations
👉 Backend testing (JUnit, Testcontainers, TDD depending on context)
👉 Deployment & CI/CD: AWS, GCP, Terraform, Jenkins, GitlabCI, Docker

I place particular importance on code readability, data exchange reliability, and the performance of distributed services.

🎨 Frontend
I also master modern stacks to effectively work on interfaces:

👉 React.js, Vue.js, Angular
👉 Next.js / Nuxt.js (personal use)
👉 TypeScript, TailwindCSS
👉 Front-end testing: React Testing Library, Vue Testing Library, Cypress

Useful for developing a feature end-to-end or collaborating closely with front-end teams.

🎯 Why work together?

✓ 5 years of experience on critical projects in Consulting Firms & Large Corporate clients
✓ Solid backend expertise + full-stack capability when needed
✓ Autonomy, clear communication, reliable deliverables
✓ Always learning: personal projects (Next, Nuxt, Nest, etc.)

👯 Need backend, data, microservices, or full-stack expertise?

I am available to discuss your project and see how I can assist you.

📩 Contact me!
  • Spanish

    Conversational

  • English

    Fluent

  • French

    Native or bilingual

  • Portuguese

    Native or bilingual

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

Experience

  • BFORBANK
    Senior Java Kafka Backend Developer
    BANKING AND INSURANCE
    August 2025 - May 2026 (9 months)
    Courbevoie, France
    **Project**: Implementation and maintenance of compliance and regulatory watch rules on the B4Bank digital banking platform


    Context:
    Within the 100% digital bank B4Bank, I was part of the team responsible for vigilance, fraud prevention, and regulatory compliance. The objective was to ensure the reliability and legal compliance of customer data within a microservices ecosystem with a strong event-driven focus (Kafka).

    Achievements:
    - Design and development of Event-Driven microservices around Kafka following the Hexagonal pattern.

    - Implementation of Avro schema in a schema registry to secure event type management.

    - Exposure and consumption of data via Kafka events.
    Implementation and maintenance of a set of business rules related to the banking domain (KYC, fraud, regulatory watch, checks).

    - Setup and optimization of Kafka Connect to synchronize topics with internal databases.

    - Setup of Kafka Stream flows for aggregating Kafka events to optimize existing flows.

    - Implementation of the Outbox pattern to ensure consistency between database insertion and Kafka event sending.

    - Development of a complete process for automated transcription of data from a Kafka topic into a file usable by the Fraud Department.

    - Transformation and validation of critical data (cleaning, enrichment, formatting) before export.

    - Contribution to improving overall code quality: code review, standardization, best practices, libraries, test coverage.


    Technical Stack:Microservices (Hexagonal pattern), Java 21, Spring boot 3, Kafka, Kafka Connect, Kafka Stream, Postgresql, Docker, Colima, Gitlab CI/CD, JUnit, Mockito, Cucumber (Integration), Maven, GCP
    Java Apache Kafka Kafka Connect Docker Microservices
  • JAX CODE
    FREELANCE DEVELOPER
    E-COMMERCE
    February 2025 - Today (1 year and 6 months)
    Aubervilliers, France
    Car Secure:Occasional support for the development of an e-commerce site.
    • Pair-programming support during the development of new features.
    • Analysis of the data model and adaptations to improve the cohesion of different tables.
    • Implementation of unit tests.
    • Salesforce integration (data synchronization via batches). Development of new front-end features.
    • Implementation of a unique payment link system.
    Technical Stack:Java 21, Quarkus, Salesforce, Next.js, React, PostgreSQL, PayTweak

    Village de Bretou:Redesign of the Wordpress website, overhauling the entire showcase site.
    • Improvement of natural referencing (SEO): Addition of tags, keywords, loading optimization, external links
    • Implementation of Google Analytics
    • Wordpress integration (content, Google Maps, Elementor components)
    • Anti-bot measures for forms using reCAPTCHA
    • Updates of various plugin versions
    Technical Stack:Wordpress, Google Analytics, Elementor
    Java Node.js Quarkus PostgreSQL Salesforce
  • PMU
    Backend Developer
    ENTERTAINMENT AND LEISURE
    September 2024 - February 2025 (5 months)
    Neuilly-sur-Seine, France
    Project: Implementation of new game servers on a Cloud platform and securing existing ones
    • Development of unit tests.
    • Creation of game servers.
    • Migration of game server rules to the new game servers.
    • Implementation of automated purge scripts by the cloud (Terraform/AWS),
    • Skill development in new areas (AWS Services, Terraform).
    • Updates on various tools through training (Angular 18, React, Vue 3, Java/Spring, Hexagonal Arch, TDD, Typescript, etc..).
    Technical Stack:Microservices architecture, Java, Spring, Terraform, AWS, Gitlab, Gitlab CI
    Java Spring Typescript Terraform Amazon Web Services

Recommendations

MG
RM
Maxime Guinchard and 1 other person have recommended Xavier

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Education

  • Master of Science
    Sorbonne Université
    2020
    Master Sciences et Technologies du Logiciel, Informatique
  • Bachelor's Degree, Computer Science
    Université Pierre et Marie Curie (Paris VI)
    2018
    Licence, Informatique

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