Senior Software Engineer (.NET / Java)

About the Opportunity Our client is a data and technology services firm serving the financial services industry. Its Colombo engineering team designs, builds, integrates, migrates and supports enterprise platforms in regulated, data-intensive environments. They are looking for Senior Software Engineers in either .NET (C#) or Java who can independently deliver features, learn complex business domains quickly, and work closely with subject matter experts. Engagements vary, so adaptability matters as much as technical depth. Role Summary You will own the delivery of features from design through production support. Depending on your stack, this includes converting legacy procedural business logic into modern Java services, or building APIs, integrations, background processing and data migrations in ASP.NET Core. You will contribute to solution design, review peers' work and maintain high engineering quality. Key Responsibilities Independently design, implement, test, document and support features that meet functional and non-functional requirements Clarify requirements, assumptions and acceptance criteria with SMEs and business analysts Analyse existing application functionality and document findings before conversion or change Build REST APIs and integrations (plus background processing for .NET) Contribute to technical design discussions and solution designs Decompose work, estimate and manage your own delivery Identify maintainability, security and operational concerns early and raise them Conduct peer code reviews and share knowledge Diagnose test and production issues, and support deployments Support data migration, validation and reconciliation activities (.NET) Build automated tests that prove converted behaviour matches the original (Java) Maintain documentation and runbooks Use approved AI coding assistants for appropriate tasks, and review and own everything they generate Learn new technologies as required, including frontend work when a project needs it Requirements Essential (both stacks) Strong engineering fundamentals: OOP, SOLID principles, design patterns, clean code and refactoring REST API development Strong SQL: query optimisation and data modelling Automated testing, root cause analysis and defect management Git and CI/CD concepts Ability to read unfamiliar codebases, understand existing functionality and learn a complex business domain quickly Degree in Computer Science, Software Engineering or a related field, or equivalent practical experience Stack-specific essentials .NET: Solid C# and modern .NET experience; ASP.NET Core; SQL Server including data migration concepts; unit and automated testing with .NET frameworks; experience in agile teams Java: Strong Java development; Spring, Maven or Gradle, JUnit and a mocking framework; JSON/XML; TDD principles; IntelliJ or similar; database performance analysis Desirable .NET: Service-oriented architecture, microservices, authentication and authorisation, background processing, Azure, containers, monitoring and observability, Infrastructure as Code, legacy modernisation or data migration experience Java: Integration patterns, SOA and event-driven concepts, Docker, Azure or AWS, experience converting procedural or legacy code into modern OO solutions Both: Frontend experience (React/TypeScript; Blazor for .NET; Angular for Java); financial services exposure Behavioural Attributes Ownership: proactive and self-driven, follows work through, raises risks early, keeps documentation current Collaboration: communicates well with stakeholders, asks questions early, challenges assumptions respectfully, shares knowledge Growth mindset: comfortable with ambiguity, learns quickly, researches solutions and keeps improving engineering practices Clear written and verbal English How the Team Works Backend focused; willingness to learn frontend work when needed is essential AI-assisted engineering with approved tools, with full ownership of the output Varied engagements across legacy conversion, API builds and integration fixes Quality built in: tests, code review, source control discipline, secure coding and documentation Information Security Comply with company and client security policies Protect confidential client and member data Report security incidents promptly Complete required security and compliance training Why This Role Ownership of meaningful features on enterprise systems in financial services Variety across conversion, API, integration and migration work Close collaboration with domain experts and a team that values quality Opportunity to shape solution design and engineering practices