Staff Engineer, Backend Developer

South West London (Hybrid) Outside IR35 £ 550 per dayThis is a unique opportunity to lead the end-to-end replacement of a business-critical premium finance platform within a regulated environment. You will take ownership from discovery through to delivery, defining the technical strategy and building the solution while ensuring uninterrupted service for customers and accurate financial reporting throughout the transition.

They are a well-established organisation operating within a highly regulated sector, delivering services to customers across the UK. Technology is central to their customer experience, with a strong focus on reliability, compliance and operational excellence. They are investing in the modernisation of a core financial integration and are seeking an experienced Staff Engineer to own this critical transformation programme.

• Map and document the existing premium finance integration landscape, including APIs, batch processes, policy lifecycle dependencies, reconciliation processes and reporting flows.
• Define and own the engineering strategy for migrating to a new third-party premium finance platform, including architecture decisions, risk management and transition planning.
• Design and build a robust integration solution using C#, .NET, SQL and modern cloud-native engineering practices.
• Deliver a migration approach supporting parallel running, phased cut-over, reconciliation between platforms and clear rollback capabilities.
• Ensure financial reporting, reconciliation, customer communications and payment collection processes remain accurate and uninterrupted throughout the transition.
• Lead vendor integration activities, testing, cut-over execution, stakeholder sign-off and knowledge transfer to the internal engineering team.

• Strong experience operating as a Staff Engineer, Principal Engineer or equivalent technical leader with ownership of large-scale platform delivery.
• Proven track record replacing or migrating business-critical third-party integrations while maintaining live operational services.
• Hands-on expertise with C#, .NET, SQL, CI/CD, Dev Ops and automated testing.
• Experience designing resilient integrations involving APIs, batch interfaces, reconciliation processes, idempotency, observability and auditability.
• Strong knowledge of Kubernetes and modern cloud-native software engineering practices.
• Experience working within regulated environments where financial accuracy, compliance and reporting are critical.
• Ability to engage effectively with technical and non-technical stakeholders and explain technical decisions clearly.
• Exposure to Azure, Azure Dev Ops, Datadog, event-driven architectures, payments, lending or financial services environments would be advantageous.