Product Engineer (Mid-Level / Senior)

You've built and run production software at a fast-growing product company. We care more about what you've built, and how you think, than about your title. Builds with AI: You use coding agents (Claude Code, Cursor or similar) every day. You delegate the implementation, never the thinking, and you own every line you merge. Product-driven: You talk to users, challenge requirements, and can show a decision that changed what you built. Engineering: You design for correctness and failure, and you've been on the hook when something broke. Ownership: You set the measure of success before building, and check that what you build achieves it. Intensity: You've chosen fast-moving, high-expectation environments before and do your best work in them. If you have experience in these areas, it's a bonus (but it's not a requirement) : TypeScript, NestJS, React/Next.js, PostgreSQL, AWS. Payments, lending or other regulated data. Energy or hardware integrations. Location: London (Holborn), 3 days/week in office. Full stack. Software runs every step of a Sunsave customer's journey: the quote, the finance application, the contract, the install, and the battery that trades energy every day. We build it in small squads, each close to a stage of that journey, with AI agents doing lots of the implementation. You'll join one of these areas, matched on your skills and interests: Acquisition: the website, the quote, the finance application and the contract Installation: getting each system designed, installed and commissioned In-life: the customer app, monitoring, maintenance and support after the install Energy: battery optimisation and grid trading Product engineers own problems end to end. You work with the people who use what you build, ship a first version in days, and engineer what the business relies on for years. We offer finance and hold customer data, so the software that runs the business must be correct, auditable and secure. We hold a high bar, and we hire engineers who raise it. We’re hiring for two levels: Product Engineer and Senior Product Engineer . As a Product Engineer, you’ll own defined problems within a feature. As a Senior Product Engineer, you’ll own a whole domain end to end, such as contracts or the customer application. You’ll design systems that stay correct as we scale, and help the engineers around you grow. Experience: at least 2 years building and running production software for Product Engineer, and at least 6 years for Senior Product Engineer. In your first interview, we'll agree which level you're going for based on your experience. Own problems end to end: You’ll own each problem, from shaping the requirements to running the solution in production, in your squad’s part of the customer journey. Start from the problem: You'll work directly with the people who do the work. You'll shape the simplest solution, and say no when a requirement solves the wrong problem. Ship early: You'll put first versions in front of real users fast, learn from real use, and drop what doesn't work. Build AI-native: You'll use agents to implement, investigate and review. You'll write the specs and context they need, and turn repeated work into skills and scripts the team reuses. Engineer what lasts: You’ll create data models that make wrong states impossible, and integrations that handle failure. You’ll write tests and evals at the right level. Run what you build: You’ll monitor what you build, set alerts on what matters, respond to incidents, and fix the cause – not just the symptom. Competitive salary Equity Private health insurance & mental health support Flexible working with an expectation to be in the London office 3 days/week Juno wellbeing monthly benefits Enhanced maternity and paternity leave 25 days holiday (excl. bank holidays) Cycle to work scheme Quarterly women's dinner/social Fortnightly company social events & Quarterly team social outing