Principal/ Senior Software Engineer

Principal/ Senior Software Engineering *Location:* *London* *Working:* *Remote* *Salary* *: £100K - £120K* About the Company We’re working with an innovative, fast-growing *FinTech* that is transforming the mortgage industry through technology and AI. The business is on a mission to make borrowing more accessible while helping mortgage brokers navigate complex affordability and risk challenges through smarter technology. Following significant growth, the company increased its annual lending volumes by *over 80% to approximately £350m in 2025* and is continuing to invest heavily in its technology and AI capabilities. The Role We’re looking for a *hands-on Technical Lead* to help shape and build the next generation of a modern lending platform. This is *not a traditional management position* . You’ll remain deeply involved in designing, building, testing and reviewing production software, while also helping shape the architecture, technical roadmap and engineering standards. *AI is at the heart of the role.* You’ll work hands-on with *LLMs, RAG, agentic workflows and AI-enabled services* , taking ideas from rapid experimentation through to secure, reliable production systems. Key Responsibilities * Design, prototype and deliver production software across the lending platform. * Build AI-powered products using *LLMs, RAG, agents and model APIs* *.* * Develop AI tools for brokers and underwriters, including decision-support systems and workflow automation. * Influence architecture and technical direction through practical experimentation and delivery. * Build scalable, secure APIs, web applications and AWS cloud-native services. * Develop robust approaches to AI evaluation, observability, safety and cost management. * Raise engineering standards through mentoring, pairing and code reviews. * Work closely with technical and non-technical stakeholders to turn complex problems into simple, practical solutions. Tech Stack *Python, React, TypeScript, Django, FastAPI, PostgreSQL, AWS, Docker, REST APIs, Git and CI/CD.* The AI stack includes *LLMs, RAG, vector search and embeddings, agentic workflows, prompt engineering, structured outputs, LLM evaluation and Amazon Bedrock.* What We’re Looking For We’re looking for someone who combines strong engineering fundamentals with genuine hands-on AI experience. You’ll ideally have: * Expert-level *Python* development skills. * Strong experience with *React and TypeScript* *.* * Strong experience with *Django and/or FastAPI* *.* * Demonstrable technical leadership through influence, delivery and mentoring. * Hands-on experience building and taking *AI/LLM systems into production* *.* * Experience working with modern AI patterns such as *RAG, agents, embeddings and LLM APIs* *.* * A pragmatic engineering mindset focused on *simplicity, maintainability, security and reliability* *.* Why Join? This is an opportunity to join a *rapidly growing FinTech where AI is genuinely central to the product strategy* , rather than simply being an experimental side project. You’ll have significant influence over the technical direction of the business while remaining hands-on with the technology. Most importantly, you’ll have the opportunity to take emerging AI technologies from *initial prototype through to real-world production* , directly impacting how the next generation of mortgage lending operates.