Senior Fullstack Engineer - Business Banking - Core Banking in London

At OakNorth, we’re on a mission to empower the UK’s most ambitious businesses. Since 2015, we’ve lent over $18 billion across the UK and US, helped create more than 58,000 new homes and 36,000 new jobs, and supported hundreds of thousands of personal savers — all while fuelling the UK economy.

The Core Banking team owns the foundational systems that power our financial products and ensure the integrity of our data and processes.

• Own the financial accounts domain, including the design, creation, and lifecycle of financial products, ensuring they are compliant, scalable, and seamlessly integrated with the ledger and third‑party systems.
• Manage our ledger (Thought Machine Vault Core), covering its integration, data integrity, and technical migrations, while maintaining a close partnership with the Thought Machine team.
• Build resilient, event‑driven systems that ensure data consistency and traceability across internal platforms and external services.
• Support financial and regulatory reporting, including reconciliations and compliance obligations such as FSCS.
• Provide the systems and data models that ensure auditability, accuracy, and trust, from customer balances to external reports.

Qualifications

The role requires:

• A strong technical background, including 5+ years of experience designing and engineering large‑scale systems.
• Measuring success in terms of business impact, not lines of code.
• Internalising the best ideas from across the organisation, humbly setting a vision that others can get behind.
• Embracing DevOps culture: you build it, you run it.
• Working well cross‑functionally and earning trust from co‑workers at all levels.
• Caring deeply about mentorship and growing your colleagues.
• Preferring simple solutions and designs over complex ones.
• Enjoying working with a diverse group of people with different areas of expertise.
• Challenging the existing approach when necessary, but also getting on board once the options have been debated and the team has made a decision.
• Being a broad thinker with the capability to see the potential impact of decisions across the wider business.
• Utilising Generative‑AI: leveraging GenAI tools to increase productivity and enhance decision‑making processes within the role.

It would be an added bonus if you have experience with or knowledge of transaction monitoring, financial crime prevention, AML, and fraud detection.

Nice to have:

• Familiarity with transaction systems, statements, and reconciliation processes.
• Experience using Thought Machine Vault Core.
• Strongly preferred: experience building and owning production Python systems.

Technology

• Python.
• PostgreSQL, BigQuery, MySQL.
• TypeScript, React, styled‑components.
• Jest, React Testing Library, Cypress, pytest.
• AWS, GCP.
• ECS Fargate, Docker, Terraform, GitHub Actions.

How we expect you to work

• Collaborate – we work in cross‑functional, mission‑driven, autonomous squads that gel over time. We pair program to work better through shared experience and knowledge.
• Focus on outcomes over outputs – solving a problem for users that translates to business results is our goal.
• Practice continuous improvement – we optimise for feedback now, rather than presuming what might be needed in the future.
• Seek to understand our users – we constantly seek understanding from data and conversations to better serve our users' needs.
• Embrace and enable continuous deployment – seamless delivery of changes into an environment is essential for us.
• Test outside‑in, test first – TDD keeps us confident in moving fast, and deploying regularly.
• You build it, you run it – we embrace DevOps culture and end‑to‑end ownership of products and features.
• Be cloud native – we leverage automation and hosted services to deliver resilient, secure services quickly and consistently.

How we expect you to behave

We embrace differences and know that when we can be ourselves at work, we are happier, more motivated, and creative. We want to be able to bring our whole selves to work, have our own perspectives and know that we belong.

• A wide range of voices heard to the benefit of all.
• Teams that are clearly happy, engaged, and laugh together.
• Perceivable safety to have an opinion or ask a question.
• No egos – people listen to and learn from others at all levels.

What makes working here better

This is a truly hybrid role, offering engineers the flexibility to work from home while also providing opportunities to collaborate in person with the team when it adds value. There’s no fixed requirement for days in the office, instead, we focus on creating space for engineers to engage meaningfully.

Work‑life balance – 25 days holiday (plus additional benefits).