Senior Full-stack Software Engineer

KEYES; Brussel Hoofdstad; On-site; EUR 70,000 - 110,000; Full time

Job summary

KEYES, a leading Belgian IT company, seeks a Senior Full-stack Software Engineer to join a major EU Institution project in Brussels. The role requires extensive JS/JEE experience to maintain and evolve core financial and operational systems.

You will visit the Brussels site up to two times per week and collaborate across multicultural teams on international projects. The ideal candidate has a bachelor degree and 10+ years IT experience, with at least 8 years in full-stack Java/JEE development.

Qualifications

• Bachelor degree
• Minimum 10 years of IT professional experience
• 8 minimum years of Full-stack Java/JEE development experience
• AWS Certified Developer - Associate or Microsoft Azure Developer Associate required
• AWS or Azure certification or hands-on AWS/Azure development experience with standard development practices

Responsibilities

• Develop front-end website architecture
• Design user interactions on web pages
• Develop back-end website applications
• Implement core business logic
• Apply data and security best practices: validation, authentication/authorization, secure storage, logging and monitoring
• Ensure web apps are optimized for performance across browsers/devices
• Design responsive applications
• Develop APIs
• Participate in scalable software design
• Maintain code integrity and organization
• Write clean, functional front- and back-end code
• Analyze data and code to troubleshoot and improve
• Perform unit/integration testing and debugging
• Deliver solutions meeting functional/non-functional requirements
• Write technical documentation
• Maintain features across the stack including UI, APIs, business logic and DB
• Deploy and manage apps on cloud with CI/CD pipelines and containers
• Bridge front-end and back-end teams for cohesive integration

Skills

Java/JEE

Full-stack development

Frontend development

Backend development

CI/CD

Education

Bachelor degree

Tools

AWS

Azure

Job description

Joining KEYES means giving purpose to your talent.

Are you looking for an environment where technology is not an end in itself, but a lever to build a sustainable future? At KEYES, we are not just looking for technical expertise; we are looking for people who share our values.

Do you want to continue your career and grow within one of Belgium’s leading IT companies?

Join KEYES as a Senior Full-Stack Software Engineer!

KEYES is a dynamic global organization that takes pride in being the trusted partner of EU Institutions. With strong commitment to excellence and a 30-years track record of delivering high-quality solutions, we are dedicated to supporting the growth and success of our clients. Our Mission is to help our clients keep up with the challenges of digital transformation by providing the right talent at the right time for the right job. To this end, we are constantly looking for talented professionals who are interested in working on challenging international projects and able to deliver high-quality results within multicultural environments. Our services include (but are not limited to) Modernization of Solutions, Digital Workspaces, Infrastructure & Cloud Solutions, Cybersecurity Solutions, Business Software Solutions, Mainframe Solutions, Data & AI Solutions, Advisory Solutions, and Staffing Solutions. Our Headquarters are in Brussels and we have active accounts and offices across Europe (i.e. Luxembourg, Athens, Brussels, etc.)

More information: www.keyes.eu

THE BACKGROUND

For our client, a European Institution based in Brussels, we are looking for an experienced Full-stack Software Engineer to join a long-term mission in a major EU Institution. For the needs of the client, you need to visit the customer in Brussels up to 2 times per week.

The ideal profile is a Java developer with 12 years in software development, maintenance, support and operations.

The principal aim of this position is to maintain, optimize, and evolutionarily develop the institution’s core financial and operational systems across the current and upcoming strategic frameworks. The role requires executing rigorous business analysis, implementing targeted technical enhancements, and managing structured change requests to guarantee long‑term operational efficiency, system stability, and continuous alignment with the evolving business requirements within established corporate frameworks and processes.

YOUR RESPONSIBILITIES:

• Development of front-end website architecture
• Design of user interactions on web pages
• Development of back-end website applications
• Implement core business logic
• Apply data and security best practices: input validation, authentication/authorization, secure storage, compliant logging and monitoring.
• Ensure web applications are optimized for performance and functionality across different browsers and devices
• Design responsive applications
• Design and develop APIs
• Participating in the design and creation of scalable software
• Maintenance of code integrity and organisation
• Writing clean, functional code on the front- and back-end
• Compile and analyse data, processes, and codes to troubleshoot problems and identify areas for improvement
• Perform unit/integration testing, debug, fix, and validate code changes
• Deliver solutions that fulfil functional and non-functional requirements and align with user expectations
• Write technical documentation
• Develop and maintain features across the entire stack, from designing user interfaces and consuming APIs to implementing server-side business logic and database interactions
• Deploy and manage applications on cloud platforms using CI/CD pipelines and containerization technologies
• Bridge the gap between front-end and back-end developers, facilitating communication and ensuring cohesive integration of all system components.

Are you the perfect match?

• Bachelor degree
• Minimum 10 years of IT professional experience
• 8 minimu years of Full-stack Java/JEE development experience
• One of the following certificiate is a requiremnet:
• AWS Certified Developer - Associate or Microsoft Azure Developer Associate
• An AWS or Azure certification
• AWS Developer Associate or Azure Developer Associate certifications. and/or Recent, hands‑on development experience with AWS or Azure, utilizing recognized software development standards in a professional environment.