Senior Java Upgrade & Migration Engineer — Remote

ALTEN; Brussel; Hybrid; EUR 90,000 - 130,000; Full time

Benefits offered by this job

Company car with fuel card

Group insurance & healthcare

Remote work possibility

Job summary

ALTEN in Belgium is hiring a Senior Java Software Developer to drive application modernization in Brussels. You will upgrade Java apps from legacy versions to modern runtimes, refactor code, and resolve migration challenges across teams.

The role requires deep Java expertise (7–21+), Spring, Tomcat and containerization with OpenShift/Kubernetes. Proficiency in English and Dutch or French is preferred, with a permanent contract and remote work options.

Qualifications

• At least 5 years of Java development experience, including Spring/Spring Boot.
• Strong Java expertise from Java 7 to Java 21+.
• Proven experience in large-scale Java upgrade and migration projects.
• Expert Java Core knowledge and enterprise app development.
• Troubleshooting across legacy architectures and complex issues.
• Experience with application servers and middleware technologies.
• Hands-on with Tomcat; OpenShift and Kubernetes are a strong asset.
• Good English; Dutch or French proficiency is a plus.

Responsibilities

• Analyze existing Java applications on legacy versions (starting from Java 7).
• Plan and execute migrations to modern Java versions (Java 17, 21+).
• Identify and resolve compatibility issues with frameworks, libraries, and servers.
• Refactor and modernize code per current Java best practices.
• Troubleshoot and resolve complex migration issues.
• Define migration strategies and roadmaps for legacy apps.
• Collaborate with development, architects, and infra teams during upgrades.
• Support testing, validation, and deployment of upgraded applications.
• Contribute to modernization of hosting environments, including containerization.

Skills

Java

Spring

Spring Boot

Java Versions 7-21

OpenShift

Kubernetes

Tomcat

CI/CD

Dutch or French

English

Tools

Tomcat

OpenShift

Kubernetes

Job description

ALTEN in Belgium is hiring a Senior Java Software Developer to drive application modernization in Brussels. You will upgrade Java apps from legacy versions to modern runtimes, refactor code, and resolve migration challenges across teams.

The role requires deep Java expertise (7–21+), Spring, Tomcat and containerization with OpenShift/Kubernetes. Proficiency in English and Dutch or French is preferred, with a permanent contract and remote work options.