Principal Software Engineer

Principal Software Engineer

Department: Tech - Software Engineering

Employment Type: Permanent - Full Time

Location: Oxford, UK

Based in Oxford, you will join a highly experienced and growing Software Development team building innovative, cloud-based software that supports major decisions in the global energy transition.

Our platform is built on AWS using a microservices architecture, with back-end services implemented in Type Script on Express

JS and AWS Lambda, and micro‑frontend user interfaces built in React.

As a Principal Software Engineer, you are a senior individual contributor operating on the technical leadership track. You will shape the technical foundations of our software platform, providing architectural leadership and long-term technical direction across multiple products and teams, without line management responsibility.

A core focus of this role is ensuring there is a clear, well architected model for integration between our products and across our wider ecosystem, enabling teams to move quickly and independently while remaining aligned.

Your success will be measured by the outcomes teams achieve with the technical direction, foundations, and guardrails you create, rather than by the volume of work you personally deliver.

This role is ideal for an engineer who wants to exert influence through technical excellence, architectural stewardship, and enablement, working in close partnership with Engineering Managers and Product leadership.

Technical strategy & architecture

• Own and evolve key elements of the software architecture across multiple products, ensuring solutions are scalable, secure, resilient, and cost‑effective
• Define and steward a clear, coherent integration architecture across our products and wider ecosystem, including principles and patterns for APIs, data ownership, and identity
• Establish and maintain architectural guardrails (standards, reference architectures, decision records) that enable teams to deliver autonomously while staying aligned
• Lead technical strategy on foundational capabilities that improve scalability, security, reliability, and engineering productivity as the organisation grows
• Influence product and engineering roadmaps by identifying systemic risks, architectural bottlenecks, and high‑leverage technical investments
• Act as a trusted technical authority for high‑impact decisions, balancing short‑term delivery needs with long‑term sustainability and total cost of ownership

Delivery & quality

• Raise the bar for operational excellence by helping teams adopt proven patterns for reliability, performance, security, and observability
• Invest in reusable foundations: tooling, libraries, templates, CI/CD improvements, and reference implementations to reduce friction and make high‑quality delivery the default
• Engage hands‑on selectively and deliberately, focusing on: de‑risking complex areas and proving out new approaches
• Champion pragmatic approaches to technical debt, helping teams make informed trade‑offs while keeping long‑term health visible and managed
• Support teams in addressing root causes of incidents and systemic issues through learning‑focused reviews, automation, and durable architectural improvements

Mentorship & influence

• Mentor senior and mid‑level engineers to strengthen architectural thinking, technical judgment, and their ability to lead complex initiatives
• Use design reviews, technical forums, pairing, and lightweight coaching to uplift capability across teams, focusing on enabling teams to solve problems independently
• Influence through clarity and collaboration: articulate technical direction, explain trade‑offs, and build alignment across teams and stakeholders
• Be intentional about where you engage, prioritising work that unblocks multiple teams, creates shared platforms, or removes recurring friction, rather than owning the most “interesting” problems yourself

Required attributes:

• Proven track record of designing, developing, and operating complex software systems that support business critical use cases
• Strong architectural experience, with evidence of shaping systems that scale across teams and…