Senior Software Engineer; Backend; m​/w​/d - Team Billing

This is us

We are a green-tech company shaping the energy industry towards a more sustainable future. At Lumenaza, you have the opportunity to actively contribute to the world of decentralized and renewable energy. Our mission is to drive the energy transition forward — with passion and innovation.

Lumenaza stands for clear values: sustainability, diversity, and collaboration. We take pride in our diverse team and are committed to supporting women in tech.

You will receive thorough onboarding into the processes of the energy market and gain access to an exciting, future‑proof industry. We are well aware of the energy market’s complexity, which is why we place great importance on sharing knowledge and ensuring that you can succeed — regardless of your previous industry experience.

We invite you to join our growing development team as a Senior Software Engineer (Backend) in the Billing team in Berlin (m/f/d).

As part of our team, you will work on solutions for the billing and monetization of energy services and the related business processes.

• Contribute to the energy transition: You design and develop software solutions that enable our customers to reliably and efficiently implement complex tariff models, billing workflows, and accounting‑related processes. Your work directly supports economically sustainable business models in renewable energy.

• Shape complex systems: From concept and implementation to quality assurance, you are involved in every step. You help design and evolve billing logic, data models, and product catalogs, ensuring long‑term maintainability, scalability, and domain correctness.

• Solve technical challenges: Billing systems place high demands on accuracy, traceability, and performance. You develop robust and scalable solutions using Python and Django
  , working on data modelling, asynchronous processing, batch processing, distributed systems, and the integration of external billing and accounting systems, while tackling demanding design and performance challenges.

• Collaborate across teams: You work closely with colleagues from backend, frontend, Dev Ops, Product Management, and adjacent domains such as Finance and Operations. Together, you design cloud‑based solutions, share knowledge, and actively shape architectural decisions. In an agile environment, you contribute to the continuous improvement of both product and processes.

• Stay curious and share knowledge: You keep up with current trends in software design, bring new ideas into the team, and support the continuous evolution of our billing platform.

• Bridge legacy and future: You help maintain existing systems while supporting their ongoing evolution and gradual modernization
  , contributing to the sustainable development of our billing and system landscape.

Do you want to help shape the energy industry of tomorrow? We value enthusiasm for sustainability over perfection — diversity and a willingness to learn are what count. Apply and help us shape the future.

• A degree in Computer Science, Business Informatics, or a comparable qualification

• At least 5 years of experience as a backend software engineer
  , ideally in domain‑complex, data‑driven systems

• Excellent knowledge of Python and Django

• Solid experience with the Django REST Framework

• Practical experience designing, developing, and integrating REST APIs

• Experience with
  microservice architectures and distributed systems

• Confident handling of Docker and Docker Compose

• Practical experience with pytest or similar testing frameworks

• Understanding of working with business‑critical legacy systems and their evolution

• Passion for clean code
  , automation, and CI/CD

• Strong communication skills in English

• Experience working with PostgreSQL
  , Redis, and object storage (e.g., S3)

• Confident use of Git

• Experience working with Linux systems

• Knowledge of Celery and asynchronous programming

• Experience with
  Pydantic, FastAPI, or Django Ninja

• Experience using the Robot Framework for test automation

• Experience integrating external accounting or ERP systems (e.g.,
  DATEV, SAP
  )

• Experience with
  Temporal or similar workflow orchestration tools

• Knowledge of Type Script and React

• German language…