Senior Python Data Engineer

We are seeking a Senior Python Data Engineer (Freelance) to join our client's ambitious migration initiative. You'll play a pivotal role in transforming legacy SAS-based ETL workloads into a modern, AI-assisted Python data platform leveraging Parquet and Spark. This is your opportunity to shape the future of data engineering by building and optimizing an agent-driven migration factory that accelerates, validates, and industrializes complex data migrations. Why This Role Matters

Our client is on a mission to modernize critical data infrastructure, unlocking agility, scalability, and long-term value. As a Senior Python Data Engineer, you will directly impact the success of this transformation by ensuring the migration process is robust, scalable, and future-proof. Your expertise will help bridge the gap between legacy systems and next-generation data platforms, driving innovation and operational excellence. Key Responsibilities

• Design, develop, and validate Python-based data transformation solutions for large-scale ETL migrations.
• Review, optimize, and refine AI-generated Python code to ensure quality, maintainability, and performance.
• Support complex migration scenarios where automated code generation requires expert intervention.
• Contribute to data quality, schema management, and Parquet optimization throughout the migration lifecycle.
• Implement and support PySpark-based solutions as needed.
• Act as a power user and contributor to the AI-assisted migration pipeline, enhancing agentic workflows and orchestration mechanisms.
• Collaborate with data engineers, architects, and SAS specialists to improve migration quality and throughput.
• Enhance human-in-the-loop validation processes and feedback loops to ensure migration accuracy and reliability.
• Identify and implement opportunities to increase automation while maintaining rigorous quality controls.

• 5+ years of hands-on Python development experience in data engineering contexts
• Expertise in Pandas, Polars, PyArrow, Parquet, and testing frameworks
• Proven experience with ETL/ELT processes, data quality controls, and schema management
• Strong knowledge of PySpark and distributed data processing (asset)
• Experience with AI-assisted development tools (e.g., GitHub Copilot) and agentic workflows
• Familiarity with agent harness engineering, workflow orchestration, and multi-agent systems
• Understanding of human-in-the-loop validation and feedback mechanisms
• Experience with SAS (asset), including DATA steps, PROC SQL, SAS macros, and ETL processing patterns
• Ability to collaborate effectively with SAS analysts and subject-matter experts

Language Proficiency

• Professional proficiency in English is required
• French or Dutch language skills are a plus

Other Requirements

• Proven track record in data engineering and migration projects
• Experience working in agile, collaborative environments
• Strong ownership mindset, problem-solving skills, and a drive for impact
• Partial remote work available; presence in Brussels as required
• This is a freelance position with a 6-month initial engagement

NIEUWTHUISWERK At RELYzIT Talent, we don't recruit - we build. We unite the top 2% of builders - engineers, architects, creators - into a movement across Europe and the GCC. Vetted through our VECTOR7 Signal Stack, you're not just hired, you're chosen. This is more than work. This is where builders build the future., Ready to build the future with RELYzIT Talent? Upload your CV and join the movement of elite builders shaping tomorrow's data platforms. #RELYzIT #TechJobs #FreelanceTalent #Brussels #Python #DataEngineering #PySpark #AI #ETL #Migration #AgenticSystems #SAS