Senior Software Engineer

• Exciting opportunity to modernise core C#/SQL systems! Extract legacy business logic, build clean services, and verify changes in shadow mode with zero downtime to revenue flows
• We are seeking a Senior Software Engineer who thrives on untangling complex systems and modernising core infrastructure without breaking production
• This is an exciting opportunity to modernise core C#/SQL systems! Extract legacy business logic, build clean services, and verify changes in shadow mode with zero downtime to revenue flows
• Extract business rules scattered across C#, embedded JavaScript and undocumented SQL stored procedures into a clean, tested, dependency-free rules assemblies
• Build new services cleanly. with proper Dependency Injection (DI), robust authentication / authorization, structured logging, and full observability
• Work fluently across both legacy .NET Framework 4.8 (ASP.NET MVC5, WebAPI 2, EF6) and modern .NET, as both will coexist for the whole transition period
• Navigate across the multiple existing systems such as the API façade, the ETL pipeline, the SNS/SQS event bus, since neither system is self-sufficient and most real bugs live in the coupling, not one side
• Deploy changes using shadow-mode verification (compute, log, and compare against legacy outcomes without writing) until equivalence is rigorously proven
• Refactor and optimise heavy SQL Server stored procedures and backend logic with total precision ensuring client-money correctness is never compromised

Benefits

• 28 Days Holiday: Relax and recharge with our enhanced allowance, plus UK bank holidays
• 4 You Days: Life can be tough. For these days employees can take a You Day each quarter, on short notice
• Hybrid Working: We value in-person collaboration. Our people are in the office multiple times a week
• Flexible Working: We are pleased to treat our employees like adults and judge them on the work they do not the hours they work
• Pension Contribution: Group Personal Pension Plan where employees contribute 5% and we contribute 5%
• Personal Development: We invest in our people, as well as yearly budget we offer external development
• Private Medical: With no financial excess and pre-existing coverage from an industry leader in physical and mental health
• Life Assurance: Our employees can rest assured that their loved ones will be supported should the worst happen
• Menopause Support: We’ve teamed up with Balance, who support those affected by all stages of the menopause
• Enhanced Allowances: From maternity leave to eyecare, we don’t just offer the basic – we make sure that we are able to go the extra mile
• Season Ticket Loans: It may not have had a big take-up during the pandemic but it’s there if our people need it
• Compassionate and Sick Leave

• Experience or comfort with golden-master testing, diffing, and shadow verification to mathematically/logically prove equivalence to legacy outputs
• Working proficiency in JavaScript/TypeScript. You’ll be interacting with both jQuery on the legacy .NET front end and modern TypeScript microservices on our sister platform
• Senior-level, hands-on experience in modern .NET (.NET 6+) paired with deep, comfortable familiarity with legacy .NET Framework 4.8 (ASP.NET MVC 5, WebAPI 2, Entity Framework 6). We need someone who respects the legacy code and is happy working in it today
• A strong “legacy technology” instinct over a “rewrite everything” approach. You favour stability, predictability, and incremental progress over shiny trends
• High proficiency in reading, understanding, and safely refactoring complex, stored-procedure-heavy database logic
• The ability to hold two disparate architectures in your head at once and reason through their edge cases, data flows, and coupling points
• Comfort operating alongside an in-house AI-agent orchestrator that supports and automates parts of our SDLC
• Hands-on experience with AWS Lambda, SQS, SNS, and RDS