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Jean-Loïc De JaegerJD

Jean-Loïc De Jaeger

Kotlin & Java Developer

€650/day
Paris, FR
8-15 years
Kotlin
Java
Spring boot
Google Cloud Platform (GCP)
Amazon Web Services

Average response time: 1 hour

Freelancer profile translated to English.
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About Jean-Loïc

I am a Kotlin & Java developer with 9 years of experience.

My specialties:
- Kotlin
- Java
- Backend Services
- GCP / Big Data / Data-Intensive Systems

I have solid experience in cloud infrastructure with Terraform:
- GCP – 5 years, with a Professional Google Cloud certification
- AWS – 1 year

I support teams and clients in delivering scalable and robust services, from data-intensive systems to modern microservices architectures.

I am interested in Senior Developer & Tech Lead roles where I can promote the adoption of good software engineering practices within the team.

Having lived in Asia for 5 years, I have developed a strong adaptability and an open approach to working in an international environment.

  • French

    Native or bilingual

  • English

    Native or bilingual

  • Chinese

    Conversational

Remote only
Primarily works remotely

Experience

  • Betclic group
    Kotlin Backend Developer
    TECH
    January 2026 - Today (5 months)
    Paris, France
    Betclic is a major player in online sports betting in Europe, offering a sports betting, poker, and horse racing platform to tens of millions of users in several regulated countries.

    Kotlin Backend Developer:
    - Development of marketing and user engagement products in Kotlin for a platform serving millions of users
    - Development of high-performance Kotlin backend microservices and APIs with Ktor, jOOQ, and PostgreSQL
    - Development of a data pipeline ingesting millions of user profiles from Snowflake to PostgreSQL via S3
    - Implementation of high-performance Kotlin microservices to support scaling and traffic peaks
    - Setup of event-driven SQS consumers in Kotlin for real-time synchronization of user data
    - Development of secure internal and back-office tools with OPA/Kong authentication
    - Resolution of data quality issues: statistical inconsistencies, SQS deduplication, and pipeline reliability
    - Setup of Gatling (Scala) load tests to validate Kotlin microservices scalability
    - Implementation of AI-assisted development (Claude Code) with custom hooks, architecture tests, and agentic code reviews to ensure quality at scale
    - Application of hexagonal architecture (Ports & Adapters) and Kotlin best practices: TDD, Arrow Either, and Datadog monitoring

    Results & Impact:
    - End-to-end delivery of the social layer of a betting platform used by tens of millions of users, from design to production
    - Reliable ingestion of 5M+ profiles with real-time statistics
    - Improvement of user data reliability
    - Implementation of a scalable event-driven architecture

    Technologies: Kotlin, Ktor, jOOQ, PostgreSQL, Snowflake, AWS SQS/S3, Gatling, Scala, Koin, Arrow, Datadog, Docker, Terraform
  • Sephora
    Senior Java Developer
    LUXURY GOODS
    March 2025 - December 2025 (9 months)
    Paris, France
    Sephora is a global beauty and cosmetics leader, offering a wide range of products through its international network of stores and online platforms.

    Senior Java Developer:
    - Development of data pipelines in Java for ingestion, transformation, and export, using Java and Apache Beam
    - Management of GCP infrastructure with Terraform to support Java data pipelines
    - Promotion of best practices to improve code quality, delivery speed, and service robustness
    - Creation of a Java CLI tool (with Vavr and GraalVM) to automatically generate boilerplate code and unit tests, increasing productivity
    - Production activities, incident resolution for Java services to ensure their reliability

    Results & Impact:
    - Delivery of high-performance Java pipelines improving data processing reliability and scalability
    - Increased development speed through a Java CLI tool automating boilerplate and test generation
    - Promotion of modern Java development practices, elevating the team's engineering standards

    Technologies: Java, GCP, Terraform, Springboot, Apache Beam, Vavr, GraalVM, BigQuery
    Java Google Cloud Platform (GCP) Terraform Apache Beam Spring boot
  • Kerfany
    Kotlin Mobile Developer
    DIGITAL AND IT
    May 2024 - Today (2 years and 1 month)
    Paris, France
    Kerfany (self-employed) — assignments at Kyaneos and AthleCare.

    Assignment: Kyaneos – Kotlin Mobile Developer (July 2025 – Present)
    Kyaneos is a French real estate investment and management company dedicated to sustainable housing and energy renovation of buildings.
    - Refactoring of the mobile application in Kotlin Multiplatform (KMP) to replace an unreliable version and improve performance and UX
    - Development of a Kotlin cross-platform application for Android and iOS with a focus on maintainable, high-quality Kotlin code
    - Implementation of an offline mode in Kotlin, allowing real estate agents to work without network coverage
    Technologies: Kotlin, Kotlin Multiplatform (KMP)

    Assignment: AthleCare – Kotlin Mobile Developer (May 2024 – June 2025)
    AthleCare is a sports-tech startup offering a mobile platform for coaches and athletes.
    - Development of a Kotlin Multiplatform (KMP) mobile application for Android and iOS, connecting coaches and athletes
    - Development of the backend in Spring Boot (Kotlin) to provide scalable APIs
    - Focus on high-quality Kotlin code, Clean Architecture, and testability
    - Optimization of cloud costs by migrating Kotlin backend workloads to GCP serverless services
    Technologies: Kotlin, Kotlin Multiplatform (KMP), Spring Boot (Kotlin), GCP
    Kotlin SpringBoot Kotlin Multiplatform Google Cloud Platform (GCP) Terraform
Check out Jean-Loïc's experience

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Education

  • Master, Embedded Systems Engineering
    ESIEE Paris
    2014
    Spécialisation : Ingénierie logicielle embarquée avec un fort accent sur les systèmes critiques dans l'aéronautique, le ferroviaire et l'automobile. Le programme couvrait : - Structures de données et algorithmes, programmation bas et haut niveau (procédurale, POO et fonctionnelle) - Bonnes pratiques d'ingénierie logicielle : automatisation des tests, TDD, principes SOLID, Clean Code, Design Patterns - Fort accent sur le développement Java à travers plusieurs couches, des systèmes embarqués aux applications Android et full-stack Technologies principales : Java, C, HTML, CSS, JavaScript
  • Exchange Program, Computer Science
    Xidian University
    2014
    Spécialisation : Informatique et Ingénierie logicielle avec un fort accent sur la programmation, les algorithmes et le system design. Le programme couvrait : - Architecture des ordinateurs - Techniques de compression de données - Introduction au Machine Learning : algorithmes classiques, techniques de traitement de données et applications pratiques - Architecture microservices Technologies principales : Java, HTML, CSS, JavaScript

Certifications

  • Professional Data Engineer – Google Cloud Platform
    Google
    2018

Skill set

Python
Scala
SQL
JavaScript
React.js

Categories