Staff Full Stack Engineer - Sell Side

Who We Are:

We are rebuilding the energy transaction, making it transparent and fair.

We're rebuilding how energy is bought and sold. That means cutting out middlemen, connecting businesses directly with renewable generators, and ensuring every transaction is traceable and transparent.

We're a 160+ person team - operators, data scientists, engineers, customer champions and energy experts - backed by top-tier investors including Lightspeed Venture Partners, Hitachi Ventures, Allianz, AlbionVC and Atomico. We closed a $75M Series B round in early 2026, taking our total funding to $94M, and we now power energy for over 4,000 UK businesses across 8,500+ sites, with over £75m in value returned to businesses and generators so far.

We're a technology company solving the energy industry, not an energy company. Some people call us a neo-utility, the neo-bank idea, applied to energy.

The industry is noticing. We were crowned Europe's Most Exciting Tech Company at the GP Bullhound Allstars awards https://www.gpbullhound.com/articles/allstars-awards-2026-winners-announced/, came in at #6 on LinkedIn's Top Startups 2026 https://www.linkedin.com/pulse/linkedin-top-startups-2026-20-uk-companies-rise-linkedin-news-uk-xoffc in the UK, #7 on the Scaling Europe 50 https://scalingeurope.co.uk/ of Europe's fastest-growing companies, and #14 on Sifted's AI 100 https://lnkd.in/p/ehxWgJyc.

Learn more about us on our website https://www.tem.energy/.

THE ROLE:

We're hiring a Staff Software Engineer to join Origination & New Products, a new three-person squad inside Sell Side Growth.

Sell Side Growth originates, contracts, and retains the renewable generators whose volume powers our platform - without generators, there's no product. The engine is scaling fast, and much of the manual process underneath today's pipeline - tendering, contracting, onboarding - needs to be rebuilt to handle that growth rather than buckle under it.

This is a deep, hands-on IC role, not a squad-lead one - that's owned by the Staff/Senior Staff engineer leading the initiative. You're free to go all-in on the hardest technical problems: integration with Rosso (our pricing and settlement engine), Control Room (our core tendering and pipeline platform), and the deal-gating risk tooling that lets us take on genuinely new categories of commercial risk safely. We're not hiring for leadership polish here. We're hiring a ridiculously good engineer.

In your first 12 months, you might:

• Own architecture-level decisions on the integration-heavy systems connecting Origination & New Products to Rosso, Data, and Billing.
• Help ship the first new product category live and generating qualified pipeline within 6 months.
• Help solve the tendering automation problem that currently limits how much volume the team can quote on - one of the highest-leverage levers for supporting our growth.
• Contribute to productising a currently manual, error-prone pricing process that's already turning away large, complex deals.
• Design deal-gating risk tooling for commercial risk categories that don't exist yet at tem, within our React/TypeScript and Python/AWS serverless stack.

RESPONSIBILITIES:

• Go deep on hard systems: Own architecture-level decisions on integration-heavy systems, reasoning clearly about boundaries, contracts, and failure modes.
• Build for ambiguity: Take a piece of an undefined, commercially-driven problem and turn it into a shippable plan, within the direction your squad lead sets.
• Work across boundaries: Deliver on dependencies that sit with teams you have no authority over, such as Rosso, Data, and Billing, getting integrations right without needing to own the relationship.
• Build with impact: Design, build, and ship the hardest parts of the new-product build sequence yourself, backend-first but comfortable moving into the React/TypeScript front end when it matters.
• Maintain high standards: Write clean, well-tested code, contribute to code reviews, and help improve team practices and documentation.

REQUIREMENTS:

Must-Haves:

• Deep technical depth in backend and systems design, with a track record of owning architecture-level decisions on complex, integration-heavy systems.
• Comfortable in our core stack: Python, AWS serverless (Lambda, API Gateway, DynamoDB, EventBridge), and event-driven architectures. React/TypeScript exposure is a plus but not the bar.
• Comfort operating without a full spec: able to take a defined slice of an ambiguous problem and turn it into a shippable plan.
• Experience delivering work where a critical dependency sits with a team you have no authority over.
• Proven product delivery experience: experience as a Full Stack or Backend Engineer in a startup or fast-paced product environment, with ownership of complex projects from start to finish.

Desirable:

• Prior experience mentoring engineers or setting technical direction, even without a formal leadership title. …