Senior Software Engineer

Senior Software Engineer - Platform & Developer Integrations (MCP) UK Remote | Permanent | High-Growth Fintech We are partnering with an ambitious, high-growth fintech that's investing heavily in AI-powered products and developer platforms. As part of that journey, they're seeking a Senior Software Engineer to help build the technology that enables AI agents to securely interact with payment systems, merchant data, and developer services. This is an exciting opportunity to work at the forefront of AI, developer tooling, and fintech, helping shape a platform that will play a critical role in the future of intelligent payments. The Opportunity AI-driven interfaces are rapidly changing how businesses and developers interact with software. Our client is building a suite of Model Context Protocol (MCP) servers that act as the trusted gateway between large language models and their payments platform, securely exposing capabilities and data to AI agents and internal tooling. As a Senior Software Engineer, you will work closely with principal engineers and a highly collaborative team to design and deliver core platform capabilities. You'll contribute to everything from authentication and session management to AI tooling, observability, and reliability. This is a hands-on engineering role within a fast-moving and emerging technology space, offering the chance to solve complex technical challenges while working with modern AI and cloud-native technologies. What You will Be Doing Designing and building components of a suite of MCP servers that expose platform capabilities to AI agents and developer tooling. Developing transport and session management capabilities, including streaming interactions, subscriptions, sampling, and user elicitation workflows.Implementing secure authentication and authorisation using OAuth 2.0, OIDC, JWT validation, and least-privilege access controls.Contributing to edge and gateway services using technologies such as Cloudflare Workers, Durable Objects, AWS Lambda, Cloud Run, or similar platforms.Building secure, scalable, and reusable services that can be adopted consistently across engineering teams.Driving quality through modern engineering practices including CI/CD, automated testing, and behavioural-driven development.Helping improve observability, performance, resilience, and operational excellence across the platform.Collaborating closely with product, engineering, security, and compliance teams to deliver impactful solutions. Your background You will be a strong backend engineer with practical experience building modern distributed systems and a genuine interest in AI-enabled applications. You will ideally bring: 6+ years of software engineering experience.Strong development experience with TypeScript/Node.js and/or Python.Experience building and consuming secure HTTP APIs and backend services.Knowledge of OAuth 2.0, OpenID Connect, JWT validation, and modern authentication patterns.Experience with cloud-native, serverless, or edge computing technologies.Strong understanding of databases, systems integration, caching, and messaging technologies.A security-conscious approach, ideally with exposure to fintech, payments, or regulated industries. AI & MCP Experience The ideal candidate will already have hands-on experience working with modern AI and agent frameworks, including: Model Context Protocol (MCP) servers, tools, resources, and prompts.Designing structured schemas that support reliable LLM interactions.Agent workflows, tool-calling patterns, and multi-step AI interactions.MCP capabilities such as elicitation and sampling.Modern AI tooling, SDKs, and LLM application development.Security considerations including prompt injection, permission boundaries, and safe AI-driven actions. Why Join? This organisation believes the best engineers thrive when they have ownership, autonomy, and the freedom to focus on solving meaningful problems. You will benefit from: A fully remote UK-based role.Exposure to one of the fastest-growing areas in software engineering.The opportunity to work alongside highly experienced engineers shaping an AI-first platform.A culture centred around innovation, collaboration, and continuous improvement.The chance to make a genuine impact within a rapidly growing fintech business. Interested? If you are an experienced software engineer with strong backend expertise and hands-on exposure to AI tooling, MCP, or agent-based systems, please apply today to learn more about the team, technology, and long-term vision behind this exciting fintech business.