We are looking for an experienced Lead Engineer (back-end) to lead the team building and scaling the infrastructure behind Scenario Builder, our electricity grid modelling platform. Scenario Builder is an in-browser platform that currently provides capacity expansion and dispatch modelling through an accessible no-code interface. The vision for Scenario Builder is to expand into power flow modelling to create a fully integrated grid modelling platform with the features and functionality needed to enable users to develop bankable scenarios that support energy investment decisions. You will line-manage a small team of engineers while remaining a highly active individual contributor. You will own the technical shape of engineering work on the back-end team — leading planning, architecture, and code quality. You will work closely with the wider product and engineering team to design, develop, and maintain the back-end services that power our platform. This hybrid role is based out of our London office near Waterloo Station and reports to the Head of Platform. Back-end development & architecture Design, develop, and maintain scalable back-end services and APIs using Python and modern frameworks (FastAPI). Design and build high-performance API endpoints to handle complex hierarchical data queries and multi-dimensional aggregations for grid modelling computations Ensure system reliability, performance, and security through best practices in code quality, testing, and monitoring. Collaborate with front-end engineers to design and implement RESTful APIs that support our web application. Collaborate with data engineers and domain experts on the evolving core data model Infrastructure & DevOps Manage and optimise cloud infrastructure (GCP) to support our computational workloads. Implement and maintain CI/CD pipelines to enable rapid, reliable deployments. Monitor system health and performance, proactively identifying and resolving issues. Implement and maintain infrastructure-as-code Technical leadership & collaboration Participate and lead in code reviews, architectural discussions, and technical planning sessions. Own technical planning: break down roadmap items into well-scoped engineering work, lead estimation, and drive architectural decision records (ADRs). Collaborate with cross-functional teams, including product, data engineering, and modelling, to deliver impactful features. Set and uphold the team's technical standards — code quality, testing strategy, API design — through direct example and code review. People & line management Line-manage a team of 3–5 engineers: run regular 1:1s, support career development, and provide timely, constructive feedback. Partner with the Head of Platform on performance reviews and personal development plans. Act as the first point of escalation for day-to-day technical blockers You should have a long-term commitment to advancing the energy transition and be driven to build robust, scalable systems that power our grid modelling platform. Passionate about creating highly performant back-end services, you understand the technical challenges associated with building niche B2B products that handle complex computational workloads. In addition to seeking out people with a proactive, problem-solving attitude and an eye for detail, as a growing organisation, collegiality and empathy for our coworkers are a requisite. While we are a rapidly growing tech startup, we are also a non-profit, so a high level of adaptability and willingness to approach challenges with creativity and curiosity is essential.