Principal Software Engineers - C# / .Net At a glance Principal Software Engineer role on a mission-critical payments platform Influence architecture, design, and delivery Flexible Hybrid working with a Belfast city centre office Strong salary, excellent benefits, and genuine technical ownership About the Company Our client is a global payment technology business operating at significant scale, powering commerce for organisations of all sizes across international markets. Their platforms process high volumes of transactions daily and are designed to operate with exceptional levels of resilience, security, and performance. With a well-established engineering presence in NI, the company continues to invest in building and evolving large-scale, high-availability systems that support critical payment flows across multiple regions. The Role The Belfast engineering team builds and maintains a high-throughput payments platform responsible for handling millions of transactions every day, where uptime, reliability, and security are non-negotiable. You'll provide senior technical leadership within the team, working hands-on across complex systems while mentoring engineers at varying levels. You'll play a key role in shaping technical direction, influencing architecture, and delivering features from a long-term product roadmap. Key Responsibilities Lead analysis, design, and development of complex, high-throughput software systems Drive best practices in unit testing, documentation, and code quality Advise on testing strategies, validation requirements, and remediation of complex issues Apply strong knowledge of engineering standards, methodologies, and PCI compliance Estimate and plan complex initiatives, projects, and technical improvements Support deployment activities across test and production environments Identify issues, assess impact, and communicate solutions clearly to technical and non-technical stakeholders Improve team effectiveness through ideas, mentoring, and technical leadership Support and coach engineers through hands-on guidance and on-the-job training What You'll need Degree in Computer Science or a related discipline 6+ years' commercial software development experience Strong experience building server-side systems in a.NET environment (C#, .NET) Experience designing and implementing scalable web services Solid experience with relational databases such as SQL Server Strong understanding of design patterns, refactoring, and object-oriented design Excellent analytical, problem-solving, and communication skills Experience working in Agile delivery environments Must be based in Northern Ireland or within commuting distance to Belfast Why Apply? Competitive salary up to £70k plus bonus Hybrid flexibility with a Belfast city centre office 26 days annual leave plus bank holidays Private medical and dental cover High trust environment with real ownership and influence Strong focus on engineering excellence and professional growth For more information on this opportunity, connect with Neill Ferguson on LinkedIn or submit your CV via the link below. Skills: c# .net sql fintech backend hybrid belfast