Principal Engineer, tem

• If you've spent your career at the intersection of high-stakes backend systems and ML productionisation, and your instinct when given a hard problem is to get into it rather than frame it, this role was written for you
• You are a Python expert. Not just comfortable in Python — you have deep expertise in building and operating production Python systems at scale
• You know the language's performance characteristics, packaging and dependency patterns, async and concurrency models, and you have opinions about how to build Python systems well
• You have genuine ML productionisation experience. You've worked at the boundary of ML and backend engineering — integrating models (forecasting, optimisation, pricing, or similar) into production systems, designing the infrastructure around them, and owning what happens when they fail or drift. This isn't coordination experience; it's hands-on engineering
• You operate at Principal level with organisation-wide impact. You've owned major technical initiatives at a high-growth startup and can point to what changed because of it. Not just influence — shipped outcomes with measurable business impact
• You have deep application architecture depth in complex domains. You've designed and evolved stateful distributed systems — APIs, event-driven architectures, data pipelines — where domain logic is the hard part. You know what domain drift looks like and how to prevent it
• You're strong with AWS serverless architecture. Hands-on experience with Lambda, API Gateway, DynamoDB, and event-driven, asynchronous workflows — operated in production and learned from failure
• You can drive to a concrete decision under ambiguity. You ask sharp questions to narrow the problem space, commit to a direction, and take responsibility for the outcome. You don't narrate a methodology — you execute one
• You connect technical decisions to business outcomes. Technical authority and business accountability aren't in tension for you — they're the same thing
• 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

Desirable

• Rosso is tem's core pricing infrastructure. It brings together forecasting, margin optimisation, and portfolio balancing to price energy tenders from first input through to signed contract — and keeps the portfolio healthy as we grow. It sits directly on the critical path for revenue
• This is a rare role. We're looking for someone who combines Principal-level distributed systems depth with real, hands-on experience bringing ML models into production — and who does all of it in Python. That combination is genuinely uncommon, and we know it
• You'll own the most complex technical deliveries in Rosso end-to-end: designing the system, writing the code, partnering with our Data Science and ML teams to get pricing and forecasting models running reliably in production, and setting the technical direction for how Rosso scales
• You'll challenge the brief, commit to a direction under uncertainty, and be accountable for outcomes — not workstreams
• Own Rosso's most complex deliveries. Lead high-impact improvements across pricing and deal-flow workflows — improving correctness, operability, and scalability as volume grows. You drive these from first design through to production
• Bridge ML and production infrastructure. This is the heart of the role. Work directly with our Data Science and ML teams to bring forecasting, optimisation, and pricing models into Rosso's core workflows safely, correctly, and at scale
• You'll co-own the design of how models integrate with production systems — not just the infrastructure wrapper around them
• Make architectural decisions that last. Design and evolve a stateful, event-driven Python system where business logic is the primary source of complexity. Set clear domain boundaries and prevent the drift that compounds over time
• Lead across teams. Drive cross-functional initiatives spanning engineering, product, data, ML, and commercial stakeholders. Align people around a technical direction and deliver
• Raise the bar. Mentor Staff and Senior Engineers, drive observability and testing standards, and act as a trusted technical voice to engineering leadership
• Plan for scale. Architect for high-volume quoting activity and large customer counts — anticipating bottlenecks before they surface in production

• Our processes normally take around 2-3 weeks from first call to offer - please let us know about any adjustments to timelines that may be required
• First call with our Talent Team (30 Mins). This is to understand your experience, motivations, and discuss the role in more detail
• Behaviour Interview with our Engineering Managers (60 Mins). This is your chance to really understand the role, the expectations, and ensure alignment on ways of working
• Technical Interviews with the Team (2 x 90 Mins). You’ll meet with potential peers in this session and will discuss technical topics and experiences
• Culture-Add Interview with Stakeholders (45 Mins). The final session will be with two cross-functional stakeholders, and will explore how your values align with ours, and is designed to be a genuine two-way conversation, your chance to understand what it’s really like to work at tem