Job Description:
NMI is a leading provider of payment gateway solutions, specialising in card-present solutions and payment processing. We are seeking a Senior Software Engineer to join our Protocols team in the UK. The Protocols team owns the services that manage connectivity between the NMI platform and external card acquirers and payment processors. These mission-critical systems, built primarily in C#, power real-time transaction processing and must operate with high levels of reliability, security, scalability, and observability. As part of the wider Payments Gateway group, the Protocols team plays a central role in ensuring seamless payment flow across our platform. As a P3 Senior Engineer, you will take ownership of complex components within this domain, contribute to architectural decisions, and guide the delivery of robust, high-performance solutions. This role is suited to engineers who operate with strong technical judgement, thrive in high-availability environments, and are motivated to continuously improve the resilience and maintainability of business-critical systems. The ideal candidate is a highly skilled software engineer with senior-level technical depth, strong system design experience, and the curiosity to work across components when needed. As a Senior Engineer, you will take ownership of complex technical challenges and play a key role in designing, developing, and evolving backend services that enable secure, performant, and reliable payment transactions. You will influence architectural decisions, proactively identify risks and technical debt, and contribute to strengthening our CI/CD, testing, and deployment practices. You are comfortable operating in high-availability environments where reliability and security are paramount. You lead by example through high engineering standards, thoughtful design, and mentorship of other engineers.
