Senior Software Engineer

NMI is building a mature, product-oriented Reliability Engineering function, and we’re looking for a Senior Software Engineer to play a key role in that evolution. This role sits on the Reliability Engineering team, which focuses on improving the reliability, performance, and operational maturity of critical platform services. The team’s mission is to move the engineering organization from reactive incident response toward intentional, engineered reliability through strong systems, tooling, and standards. As a Senior Engineer, you will operate beyond a single service or codebase, designing and building reliability frameworks, platform capabilities, and guardrails that improve uptime, observability, and operational confidence. This is a highly hands-on role with strong expectations around technical leadership, ownership, and delivery. Key Responsibilities: Design and build reliability-focused frameworks, tooling, and standards that improve platform uptime, performance, and operational confidence. Drive initiatives that move reliability from reactive response to proactive engineering, emphasizing prevention, early detection, and fast recovery. Partner with engineering teams to embed reliability into system design, development practices, and deployment workflows. Establish and evolve observability practices, including metrics, logging, alerting, and dashboards that enable clear operational insight. Identify systemic risks and failure patterns, and lead efforts to address them through automation, architectural improvements, and process refinement. Contribute hands-on to production codebases, internal tools, and platform services with a focus on long-term maintainability. Influence technical direction across teams through design reviews, technical proposals, and clear written communication. Improve operational maturity through better incident practices, post-incident learning, and continuous improvement loops. Mentor engineers by modeling strong ownership, technical judgment, and disciplined delivery. Participate in on-call rotations, with a clear mandate to reduce operational load over time through engineering. Skills & Experience: 6+ years of experience building and operating production-grade software systems in complex environments. Strong experience developing backend services in PHP, with the ability and desire to work language-agnostically and quickly learn new languages, frameworks, and codebases as needed. Proven experience working on reliable, scalable, and highly available systems, with a clear understanding of tradeoffs in performance, resilience, and maintainability. Practical experience designing or contributing to platform-level reliability solutions, such as observability tooling, alerting strategies, or reliability standards. Solid understanding of distributed system fundamentals, including failure modes, latency, capacity, and graceful degradation. Experience defining and improving operational practices, including incident response, post-incident reviews, and preventative engineering. Strong knowledge of relational databases and data access patterns, with an operational mindset toward performance and reliability. Hands-on experience deploying and operating services in cloud environments (AWS or equivalent). Familiarity with secure, compliance-aware development practices (eg: PCI, SOC 2, OWASP). Ability to influence technical direction across teams through clear communication, sound judgment, and collaboration. As well as being a part of something exciting everyday, you will also receive the following benefits: Annual bonus scheme dependent on individual and company performance Annual salary of £50,000 - £60,000 25 days holiday each year (+ bank holidays + 1 day after each year of service with up to a max. of 30 days) Workplace pension scheme Private medical insurance (upon 30 days of employment) 7 hours per day, 35 hours per week A remote first culture Great work-life balance with our Flexi-time policy Family Friendly policies (Enhanced Maternity and Paternity Pay and Shared Parental Leave). A chance to develop with an allocated company training budget Bike2Work Scheme Lifeworks, an Employee Assistance Programme which offers wellbeing, family and financial support services, such as assessments, resources and even 1:1 counselling sessions. It also offers interesting perks such as discounts on gyms, restaurants, high street retailers and cinema tickets A strong commitment to employee wellbeing including mental health first aiders Employee referral scheme with generous financial reward Bonusly colleague reward scheme What we do! NMI enables our partners with choice, and challenges the one-size-fits-all approach to payments. You've probably used NMI in the last 24 hours without even realizing it. We’re the platform that powers success for innovative tech created by SMBs, entrepreneurs and fintech startups. We’re creative problem solvers who help visionaries smash through boundaries and think beyond what’s possible so they can think about what’s next. But we’re not just built for the tech savvy. We democratize the latest payments technology so that everyone can realize the benefits of easy payments across the full spectrum of commerce. We’re all about enabling more payments in more ways and more places. We believe that having a diverse group of employees strengthens both our work and our workplace. We’re focused on making NMI more diverse and welcoming with initiatives like having a dedicated Diversity, Equity & Inclusion action group, diversity goals for hiring, anonymized resume screening, affinity groups such as our Women's network and LGBTQ+ Network, open forums for discussions on diversity and social justice, and measuring inclusion and belonging as part of our regular employee engagement surveys. Equal Opportunity NMI is committed to providing equal employment opportunity for all persons regardless of race, color, religion, sex, age, marital status, national origin, sexual orientation or sexual identity, genetic information, citizen status (except those that do not have the legal right to be employed in the United States), disability, military service, service member, veteran status, or any other basis protected by applicable law. Please be aware that all offers of employment are made subject to receipt of satisfactory background and financial checks. Attention job applicants: Please note that in compliance with the data protection regulations within your jurisdiction, any personal information submitted with your job application may be collected and used by NMI for the purpose of recruitment and employment-related activities. By submitting your application, you acknowledge and provide explicit consent to the processing of your personal information as described in our privacy policy found on our website. For more information on how we process your information, please read our privacy policy here: https://www.nmi.com/legal/privacy-policy/ #LI-Remote Salary range, depending on experience: £50,000 — £60,000 GBP