API Developer & Gateway Administrator (Freelance)

Location: Brussels, Belgium (Hybrid: 2-3 days remote per week) Type: Freelance Contract Experience Level: Senior / Expert (10+ years of experience) Languages: French or Dutch (Professional working proficiency, min. 3/4) OR English (Professional working proficiency, min. 3/4) About Smile 🌟 Passionate about tech, digital, and innovation?

Join the 1,800 employees at Smile , the European leader in open-source integration, spread across 20 agencies in 9 countries. Collaborative spirit and knowledge sharing are at the heart of our DNA. Our experts push the boundaries of open source every day to build a smarter, more efficient, and more responsible digital world.

Here, we don't just follow trends, we create them! Join Smile in Brussels and take part in projects that truly matter! 🏆 The Opportunity On behalf of our client—a major player in their sector based in Brussels—we are looking for an outstanding Senior API Developer & Gateway Administrator on a freelance basis. In this role, you will act as a key technical expert, driving the development, configuration, and secure deployment of critical API gateways.

You will play a vital role in building modern, scalable, and highly secure integration architectures in a collaborative, Agile environment.

Your Responsibilities

Design, build, and deploy secure API Gateways, specializing in Axway (or equivalent enterprise suites like Apigee/WSO2). API Design: Define and implement robust OpenAPI specifications, promoting modern SOA/REST architectural patterns. API Security & Identity: Implement and enforce industry-standard security protocols, including OAuth2, JWT, PKI, and secure web services.

Vulnerability & Testing: Proactively manage API security posture utilizing tools like Snyk and conduct comprehensive web service testing. Modern Lifecycle & Automation: Integrate your developments within public cloud infrastructures and CI/CD pipelines, utilizing Git for version control. Agile Collaboration: Participate actively in Agile ceremonies, using Jira and Confluence for progress tracking and high-quality technical documentation.

Your Profile

Senior profile with 10+ years of hands-on experience in IT integration, with a strong focus on API gateway development and security. Core Technical Expertise: Solid experience with API Gateway platforms (specifically Axway , or alternatively Apigee or WSO2 ). Mastery of API standards, SOA/REST architecture, and data formats (XML/JSON).

Strong command of API security frameworks and tools ( JWT, OAuth2, PKI, Snyk ). Hands-on experience with Public Cloud environments, CI/CD automation pipelines, and Git . Experience in automated web services testing. Methodology: Proven experience working within an Agile framework utilizing Jira and Confluence . Languages: Professional working proficiency (3/4) in either Dutch , French , or English .

Why Smile? 😊 Proximity Management: Our proximity management by peers fosters dialogue and the implementation of a tailored career path. Continuous Growth: Because the digital sector is in constant motion, Smile is committed to making you an expert in your field, thanks to a comprehensive training offer: access to an e-learning platform, financing of certifications, and dedicated knowledge-sharing tools.

Vibrant Community: Your year will be animated by group and agency events: annual convention, participation in trade fairs, summer party, and both formal & informal afterworks. The Next Steps 🚀 First Contact: A phone call to discuss your aspirations and what we can offer you. Meeting: An opportunity to get to know each other and explore your professional background.

Business Interview: A discussion with one of our experts to assess your skills and define your goals.