Senior Backend Engineer - Python

Octopus Energy started with a bold idea: to build Britain's first truly digital energy supplier.By combining world-class tech with brilliant humans who care deeply about customers and driving the renewable energy transition, we made it happen and in 2025, we became Britain's largest energy supplier.In 2021, we brought this mission to Japan – the world’s largest liberalised energy market. Here, we are committed to making energy better for both customers and the planet, while driving the growth of green energy across the country by using smart technology. In our lean and fast-moving team in Japan, every idea and action has the power to create a real impact on both business and society. We’re looking for people who can build scalable, highly resilient platforms from the ground up.We're scaling fast, and building the next generation of products to accelerate the green energy transition. Senior engineers will lead architectural decisions, guide system design, and mentor engineers as we scale. From making it effortless to switch to heat pumps, solar and EVs, to launching smart tariffs and creating renewable generation at scale, we're solving some of the most complex challenges in energy with speed, creativity and customer obsession. Here in Japan we’re following in the footsteps of the UK, taking their learnings, and adopting products and experiences that customers love.As a member of the Octopus Tech Team, you'll have real ownership, variety, and the chance to shape products that make a tangible difference in people's lives – lowering bills, enabling greener living, and delivering experiences customers genuinely love. We’re expecting senior technical leadership, you will have tech decision-making authority, lead initiatives across domains, solve deep technical challenges, and align with global tech strategy. But you won’t be alone, you'll work side by side with teams across customer service, sales & marketing, operations, finance and data, and see the impact of your work in the real world, fast. You will also be a member of our global engineering community, where support is just a Google Meets or Slack message away.We’re looking for people who want to take part in this journey and help shape the future of energy in Japan. If this sounds exciting, we'd love to chat.There’s a couple of things you should be aware of about this role. You may initially be employed by Kraken Tech Japan, our sister company in Japan, then, at some future time in the near future, transfer your employment to Octopus along with other tech staff in our other markets across the world.We’re expanding the scope of our tech team, and we are looking for Backend Engineers to join our team to lead backend development on some exciting new products. You will play a key role in leading the backend domain and building scalable, reliable services that power the future of energy in Japan.

What You'll Do

• Build and operate Octopus Energy products for the Japanese market (with many on the horizon). Including driving architectural decisions, improving reliability and performance, and aligning global tech strategy with local requirements
• Design and develop APIs to integrate with other systems and services. For example, lead API design standards, review complex integrations, and ensure consistency across services
• Collaborate with international teams (UK, EU, APAC and USA) in global development projects
• Develop and operate Octopus Energy’s core global backend system

What You'll Need

• 5+ years of professional experience in backend web application development
• Hands-on experience with Python/Django or equivalent web frameworks
• Architectural understanding, best practices, system decomposition, and mentoring others
• Experience designing and operating RDBMS (, PostgreSQL, MySQL)
• Experience in team development using Git
• Experience with secure, reliable, large-scale/ high-transaction systems
• Experience developing and operating systems in cloud environments (AWS, GCP, or Azure)
• Experience with microservice architecture
• Ability to communicate in English (participating in meetings and discussions, reading and writing)
• Interest in environmental issues and the energy industry

What we're looking for:

• A self-sufficient person with a high level of initiative and who enjoys working in a fast-changing environment and can work autonomously
• A strong team player who collaborates across teams and departments
• Someone excited to solve social challenges through technology.
• Ability to communicate in English is essential

We're looking for someone with a general interest in technology and problem-solving; someone diligent and thoughtful. It would be helpful to have experience/expertise in the following (in rough priority order):

• Python
• Django (or equiv. web framework)
• Domain modelling
• Designing distributed systems, improving service reliability, and shaping long-term architectural strategy.
• HTTP and REST APIs, GraphQL and other API technologies
• Writing robust and fault-tolerant software
• Celery and async processing
• Postgres

Plus experience in the following would be a bonus:

• AWS
• Terraform, Packer, Consul
• Ability to speak Japanese would be a plus

Our process usually takes up to 4 weeks, but we’ll always do our best to flex around what works for you. Along the way, you’ll chat with our recruitment team and your Recruiter will help you throughout different stages. Got any burning questions before then? Drop us a message at and we’d love to help!If this sounds like you then we'd love to hear from you. 🚀Are you ready for a career with us? We want to ensure you have all the tools and environment you need to unleash your potential. Need any specific accommodations? Whether you require specific accommodations or have a unique preference, let us know, and we'll do what we can to customise your interview process for comfort and maximum magic!Studies have shown that some groups of people, like women, are less likely to apply to a role unless they meet 100% of the job requirements. Whoever you are, if you like one of our jobs, we encourage you to apply as you might just be the candidate we hire. Across Octopus, we're looking for genuinely decent people who are honest and empathetic. Our people are our strongest asset and the unique skills and perspectives people bring to the team are the driving force of our success. As an equal opportunity employer, we do not discriminate on the basis of any protected attribute. Our commitment is to provide equal opportunities, an inclusive work environment, and fairness for everyone.We may use artificial intelligence (AI) tools to support parts of the hiring process, such as reviewing applications, analyzing resumes, or assessing responses. These tools assist our recruitment team but do not replace human judgment. Final hiring decisions are ultimately made by humans. If you would like more information about how your data is processed, please contact us.