Principal Engineer - Pricing Infrastructure in London

Who We Are: We are rebuilding the energy transaction, making it transparent and fair. Our goal is to put power back where it belongs, in the hands of customers and to take on one of the most critical problems of our century, access to low cost electricity. tem exists to fix a broken global energy market that’s long favoured legacy operators, intermediaries, and opaque pricing. Today’s electricity system was not designed for rapid decarbonisation, AI-driven efficiency or fair access for the actual users - businesses and generators. We’ve built the first AI native transaction infrastructure to reinvent how electricity is bought, sold and priced. Our technology is designed to cut out the inefficient fees, automate complex market flows, and bring transparency and fairness to energy transactions at scale. In late 2025, after extraordinary growth, we closed a $75 million Series B - led by Lightspeed Venture Partners with participation from Albion, Atomico, Allianz, Hitachi Ventures, Schroders Capital and others - positioning us for global expansion, deeper product innovation and category leadership. We’re scaling internationally and building toward a future where AI-driven infrastructure is foundational to electricity markets worldwide. Since launch, our modern utility product, known as RED, has already facilitated thousands of business customers and billions in energy transaction value, proving that modern software and AI can transform an industry built on legacy systems. At tem, we’re not just building another energy company, we’re rearchitecting market infrastructure so that transparency, efficiency and sustainability become the default, not the exception.

The Role: We are looking for a Senior Staff Engineer to help shape and scale Rosso: tem’s core IP transaction infrastructure that saves our customers millions. Rosso brings together forecasting, margin and portfolio optimisation to price tender inputs through to contract, while keeping the portfolio balanced as we grow. Rosso sits on the critical path for revenue and customer experience. The problem space is complex and high stakes, with interdependent business rules, stateful workflows, and tight coupling between technical decisions and commercial outcomes. You will join a team with strong product vision and technical leadership, and you will play a key strategic role in tendering and the deal flow that drives it, bringing senior execution strength. This means owning complex deliveries end-to-end, raising system quality and reliability, and preventing domain drift as the platform and organisation scale. This role combines deep hands‑on engineering with strategic technical ownership and organisational influence.

Responsibilities:

• Drive Technical Leadership through Execution: Alongside Principal Engineers, you will lead and ship high-impact improvements across Rosso workflows, improving correctness, operability and scalability as volume and complexity grow.
• Drive Multi‑Team Initiatives: Lead complex, cross-functional efforts across teams and systems - aligning stakeholders and delivering high‑leverage outcomes.
• Build & Ship: Continue being deeply hands‑on in designing, coding, and reviewing critical components across stateful backend services, APIs, and infrastructure.
• Strengthen Foundations: Improve reliability and operability, observability, testing strategy, and deployment practices - driving monitoring of service objectives, incident reduction, and operational excellence.
• Integrate machine learning models into production: Partner with ML/Data teams to productionise a range of models (including forecasting, optimisation and pricing) safely and effectively within core Rosso workflows.
• Design for correctness in complex workflows: Build and evolve pricing and deal‑flow workflows where consistency and failure handling are first‑class concerns.
• Prevent domain drift: Create and maintain clear domain boundaries, shared language, and reduce compounding complexity over time.
• Multiply Impact: Mentor Staff and Senior Engineers, raise engineering standards, and act as a trusted technical advisor to leadership.
• Plan for Scale: Architect systems to handle high‑volume quoting/pricing activity and large customer counts, anticipating bottlenecks before they emerge.

Requirements:

Must‑Haves:

• Exceptional technical leadership experience: Experience operating at Staff+ or Senior Staff level, with clear evidence of organisation‑wide impact at a high‑growth startup.
• Architectural depth: Proven ability to design and evolve complex, stateful distributed systems spanning APIs, event‑driven architectures, data systems, and front‑end applications - where domain logic is the primary source of complexity. Proven patterns for high‑throughput performance and scaling architecture to support hundreds of thousands of customers, while preventing domain drift.
• Multi‑team influence: Experience leading cross‑team initiatives that directly impact revenue across engineering, product, data, machine learning, commercial and ops stakeholders.
• Modern tech expertise: Deep experience with Python, AWS serverless architecture (Lambda, API Gateway, DynamoDB), Event‑driven systems and asynchronous workflows.
• Data + domain modelling strength: Strong ability in data modelling for complex, interdependent business rules, including correctness, consistency, and designing for failure modes.
• Product & business alignment: Demonstrated ability to connect technical decisions to business outcomes and customer experience.
• First‑principles problem solving: Ability to reason from fundamentals (constraints, incentives, data and system behaviour) to design solutions in complex, high‑stakes domains.
• Navigating ambiguity: Comfort operating in evolving environments, defining direction where it doesn’t yet exist.

Desirable:

• Experience in high‑performance / high‑scale environments (bonus if you’ve used tools like Kubernetes, Spark, or similar).
• Delivered a large, complex initiative end‑to‑end (greenfield or major redesign) with clear business impact.
• Experience scaling systems from early product‑market fit to multi‑product platforms.
• Experience working closely or as part of Machine Learning teams.
• Exposure to regulated industries (e.g., energy, fintech, govtech).
• Familiarity with real‑time pricing engines, workflow orchestration, or AI/agentic systems.
• Experience improving engineering org design, team topology, or platform strategy.

Benefits & Perks:

• Competitive salary: We review salaries twice a year using real‑time market data, with transparent, consistent pay for the same role and level.
• Stock Options: everyone on the team has ownership in our mission.
• 25 days holiday + public holidays: Swap public holidays for ones that matter most to you. Plus, get an extra day off for your birthday.
• Remote & flexible working: We’re fully remote with clear core hours, and no internal meetings on Friday afternoons.
• Home working & wellbeing budgets: Up to £1,200 / €1,200 annually to upgrade your remote setup (co‑working passes, equipment, etc.). Up to £150 / €150 monthly on anything that supports your wellbeing – from therapy to gym memberships to meditation apps.

We welcome applications from people of all backgrounds, experiences, and identities, including those that are traditionally underrepresented in the tech and energy sectors. If you’re excited about this role but not sure you meet every requirement, we’d still love to hear from you. Your unique perspective could be exactly what we’re looking for.