Core System Developer (Delphi / C# / Oracle PL/SQL)

Location : Bielefeld Area, Germany (10 visits onsite only) Languages Required : German Fluent + English Fluent 1. Role Overview We are looking for two skilled Core Systems Developers to help stabilize, modernize, and de-risk a business-critical legacy core system. You will focus on maintaining organically grown codebases, implementing regulatory/compliance updates (e.g., German Heating Costs Ordinance / HKVO), managing build/release cycles, executing shadow testing, and driving knowledge documentation for long-term system continuity. 2. Key Responsibilities · Core Code Maintenance: Develop, review, and maintain business-critical code across Delphi, C#, and Oracle PL/SQL environments. · Regulatory & Business Logic: Implement complex mathematical, domain-specific, and regulatory code changes (including HKVO standards). · L3 Support & Root Cause Analysis: Diagnose complex system defects, perform in-depth code debugging, and deliver permanent technical resolutions. · System Coverage & Architecture: Cover critical domains across application code, data, and interfaces; document architecture for knowledge transfer. · Build, Release & Migration: Take ownership of build/release pipelines, execute shadow testing, and support future system modernization/migration initiatives. 3. Qualifications & Technical Requirements Must-Have Requirements: · Core Stack Expertise: o Several years of development experience with Delphi. o Very good knowledge of Oracle PL/SQL and relational database concepts. o Strong hands-on development experience with C#. · System Experience: Proven track record in maintaining and refactoring large, monolithic, or legacy Windows-based applications. · Debugging & Analysis: Proficient in deep technical debugging, root cause analysis, and object-oriented software design. · Analytical Skills: Strong mathematical knowledge and conceptual skills to translate complex domain logic into clean code. · Languages: Fluent German (written & spoken) and good technical English. · Location: Willingness to work regularly on-site in the Bielefeld area. Nice-to-Have Requirements: · Knowledge of the German Heating Costs Ordinance (HKVO) or experience in the housing/energy sector. · Experience with print technologies (PCL, PostScript, PDF) or PostgreSQL. · Familiarity with TFS, Git, automated testing, code reviews, and interface development (REST/SOAP). · Exposure to database performance tuning or AI-assisted development tools.