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Sami ChajiiSC

Sami Chajii

Senior Java Backend Engineer

500 €/jour
Brussels, BE
3-7 ans

Délai de réponse moyen : 1h

À propos de Sami

Hi! I’m Sami — a Senior Java Backend Engineer with 5+ years of experience building high-performance backend systems, APIs, and microservices for banks and fintech companies.

I’ve worked for Crelan, AXA Bank, and ING Belgium as a consultant, where I helped deliver major system integrations, build secure APIs, and design scalable backend architectures.

💼 What I can do for you

✔ Java backend development (Quarkus, Spring Boot, Jakarta EE)
✔ REST API design & implementation
✔ Microservices architecture (clean, modular, scalable)
✔ Messaging systems (Kafka, async flows, event-driven systems)
✔ Batch processing (Java or C-based high-volume batches)
✔ Database design (PostgreSQL, Oracle, MySQL)
✔ CI/CD & DevOps support
✔ Refactoring legacy systems (COBOL → modern stack, C#, Java)
✔ Debugging, performance tuning & production support Banking & enterprise experience

I’ve delivered critical features for:
-Core banking systems
-Authentication & customer data management
-Internal orchestration services
-Data migration across legacy systems
-Real-time communication between distributed services Tech Stack Java, Quarkus, Spring --Boot, Kafka, REST, Microservices, Docker, Git, C/C++, Python, C#, SQL, Linux


💡 Why clients hire me:
-I work fast and deliver clean, maintainable code
-I understand complex enterprise systems (banking, VR, embedded)
-I’m flexible: from quick fixes to complete backend architecture
-I communicate clearly and reliably

If you need a strong backend engineer who delivers real value, I’m ready to help.

Let’s build something great together.
  • Anglais

    Bilingue ou natif

  • Français

    Bilingue ou natif

  • Italien

    Bilingue ou natif

  • Arabe

    Capacité professionnelle complète

Accepte de travailler sur site
Brussels (jusqu’à 50 km)

Expériences

  • Mainsys
    SOFTWARE ENGINEER
    janvier 2023 - Aujourd'hui (3 ans et 5 mois)
    Brussels, Belgium
    • Key contributor to the core banking system integration during the Crelan–AXA merger, delivering stable and scalable backend services.
    • Designed, developed, and maintained multiple Java REST APIs using Quarkus, applying clean architecture, dependency injection, and reactive programming.
    • Implemented microservices for core banking features, including authentication flows, customer data management, and internal orchestration services.
    • Built asynchronous processing components using messaging technologies (Kafka).
    • Created and optimized batch processing modules in C, supporting data migration and transformation between systems.
    • Performed code reviews, contributed to CI/CD improvements, and enforced best practices for clean code and backend performance.
    • Collaborated with DevOps and product teams to deploy, monitor, and troubleshoot backend services in production environments.
    • Analyzed and translated COBOL applications into C#.
    Java COBOL Traitement par batchs Quarkus C#
  • Virtual Park
    R&D ENGINEER
    janvier 2021 - janvier 2023 (2 ans)
    Belgium
    • State-of-the art of VR (virtual reality) technologies in scientific literature.
    • Study and analysis of VR technologies (e.g., tracking systems, haptic technologies).
    • Software developer (JAVA, Python, C#).
    • Embedded Linux on Raspbian and Ubuntu.
    • Developed the database for the newly I/O system installed and the communication between clients and server.
    • Design of the network distribution of an attraction park.
    • Designed and implemented RESTful APIs with Java (Spring Boot) for the new web platform of the company.
    • Project executive. Design, implementation and testing of an airflow generator made of amplifiers, speakers and controlled by a Raspberry Pi.
    Java Python C#
  • HAEMERS
    Project Assistant Engineer
    juillet 2019 - septembre 2019 (2 mois)
    Brussels, Belgique
    • Stage as Assistant Engineer of 2 months. working on Database (sqlite3 python) on Raspberry and in electronics circuits.
    • Contact the sellers and search the electronic components.
    • Developed the database for the newly I/O system installed. This is able to recollect the data from the sensors, send it to a central server who will then store the values in the database each hour.
    • Developed an GUI in JAVA representing the sensors on the field.
    • Design and implement a PCB to have a better connection between the sensors and the µC.

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Formations

  • MBA DIPLOMA
    Université libre de Bruxelles Ecole Polytechnique
    2021
    MBA DIPLOMA
  • BACHELOR DEGREE
    Université libre de Bruxelles Ecole Polytechnique
    2019
    BACHELOR DEGREE

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