Staff Engineer (Global Billing, Payments & API)

Location: London, Bristol or Edinburgh, UK (hybrid, three days a week in the office) Level: Staff Engineer TL2 Team: Global Billing, Payments & API Salary: £97,000 – £122,000 + discretionary bonus Contract: Permanent Reporting To: Senior Software Engineering Manager Please note: This role requires an existing right to work in the UK. We can’t offer visa sponsorship, but we review sponsorship role by role, so keep an eye on our careers site for future opportunities. About Kaluza Kaluza is the Energy Intelligence Platform, turning energy complexity into seamless coordination. We help energy companies overcome today’s challenges while accelerating the shift to a clean, electrified future. Our platform orchestrates millions of real-time decisions across homes, devices, markets and grids. By combining predictive algorithms with human-centred design, Kaluza makes clean energy dependable, affordable and adaptive to everyday life. With teams across Europe, Asia and Australia, and a joint venture with Mitsubishi Corporation in Japan, we power leading companies including OVO, AGL and ENGIE, as well as innovators like Volvo and Volkswagen. What you'll do Kaluza runs the billing and payments engine behind some of the world's biggest energy retailers. This role builds and evolves the platform other engineering teams build on top of: the shared APIs, integration patterns, and technical standards that let billing and payments capability get built once and reused everywhere, instead of rebuilt separately for every new market or client relationship. That matters because of where Kaluza is headed: as we grow into new markets and take on more of the world's largest energy retailers as clients, having a consistent, well-designed API platform is what lets new capability get adopted quickly and safely across every team that needs it, rather than each team solving integration and standards problems on its own. Getting this right directly shapes how fast Kaluza can extend billing and payments capability to new markets and clients. We're also in the middle of reorganising how this part of the business works, moving toward one shared global core that every market configures rather than rebuilds. This role's remit, API platform and standards, is one of the technical foundations that shift depends on. Responsibilities include: • You'll own system design and architecture for the API Platform and Standards squad, not just a single service. • You'll create and challenge product and engineering proposals, backing design trade-offs with data. • You'll diagnose and resolve complex technical and product issues, including in areas outside your immediate domain. • You'll establish architectural patterns and technical standards that other teams build on top of. • You'll take ambiguous, loosely-defined technical requirements and turn them into a concrete plan others can execute against. • You'll influence engineering leadership, product, and adjacent squads to bring clarity and alignment on technical direction. • You'll mentor and upskill engineers beyond your immediate team, contributing to a wider learning culture. What you'll bring Ideally you’ll have: • Deep technical expertise applied to system design and architecture ownership across a squad, not just a single team or service. • Be able to create and challenge product and engineering proposals and make design trade-offs, backed by data. • A track record diagnosing and resolving complex technical and product issues, including in domains you aren't already close to. • Be skilled at establishing and driving adoption of architectural patterns and technical standards that other teams build on top of. • Be comfortable taking ambiguous, loosely-defined technical requirements and turning them i