Senior Software Engineer (Fullstack) (m/w/d)

This is us Building the digital infrastructure for a new renewable energy system Lumenaza builds this digital infrastructure. Our platform connects renewable generation, dynamic tariffs, energy-market processes, and the processing of large volumes of complex energy data. This enables utilities and new market participants to operate decentralized and renewable business models in everyday practice. We are driven by a clear mission: accelerating the transition to a sustainable energy system. At the same time, we value diversity, collaboration, and continuous learning. Your tasks Your Role As a Senior Engineer (Fullstack), you will design and build core systems that power real-world energy processes - from billing to market communication. You take ownership of complex domains, contribute to architectural decisions, and help evolve both our systems and engineering practices. What You’ll Do Build and own core backend systems Design and implement scalable solutions for billing, tariff models and energy market processes.Shape system architecture Work across the full lifecycle - from design to deployment - ensuring maintainability, scalability, and correctness.Solve complex technical challenges Develop robust solutions involving data modeling, asynchronous processing, and distributed systems.Collaborate across disciplines Work closely with Product, Frontend and DevOps to deliver cloud-based solutions and improve our platform.Drive improvement and innovation Bring in new ideas, improve engineering practices and explore modern development approaches, including AI-assisted workflows.Modernize existing systems Help evolve and migrate legacy systems toward modern architectures. Your profile Core Requirements 5+ years of backend development experienceStrong Python and Django expertiseExperience designing and building REST APIsExperience with distributed systems / microservicesSolid understanding of databases (PostgreSQL)Experience with Docker and CI/CD workflowsExcellent communication skills in English Nice to Have Experience with FastAPI, Pydantic, or Django NinjaKnowledge of Celery or similar async toolsExperience integrating external systems (e.g. ERP, APIs)Familiarity with React / TypeScriptInterest in energy markets or regulated domains Our Tech Stack Python, Django, Django REST FrameworkPostgreSQL, RedisCelery (async processing)Docker, KubernetesGitLab CI/CDRobot Framework (testing)React (frontend) We deploy continuously to Kubernetes and work with distributed systems handling complex, business-critical data. We offer you this Impact: Build software that directly enables renewable energy business modelsOwnership: Work on complex, meaningful systems with real-world impactGrowth: Structured onboarding and continuous learningFlexibility: Flexible hours and hybrid work setup (up to 2 days / week at the office)Benefits: Competitive compensation, DeutschlandticketLocation: Modern office in Berlin Kreuzberg You do not meet every technical requirement 100%, but you recognize yourself in the role and our mission? Then we look forward to receiving your application. About Us Lumenaza GmbH, through its brand Lumenaza.Community, is a leading provider of direct marketing for small-scale installations and a supplier of electricity for household tariffs ranging from fixed to dynamic contracts. The Lumenaza Community represents green, decentralized electricity generation. Since 2013, Lumenaza GmbH has also been supporting major energy supply companies such as EnBW and E.ON as a software and service provider, offering innovative solutions in billing, market communication, and virtual power plants. For more information, visit Lumenaza.Community and www.lumenaza.com.