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 usually respond within two weeks
Impact and Responsibilities
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.
What we're looking for in you
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.
High proficiency in reading, understanding, and safely refactoring complex, stored-procedure-heavy database logic.
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.
A strong "legacy technology" instinct over a "rewrite everything" approach. You favour stability, predictability, and incremental progress over shiny trends.
Experience or comfort with golden-master testing, diffing, and shadow verification to mathematically/logically prove equivalence to legacy outputs.
The ability to hold two disparate architectures in your head at once and reason through their edge cases, data flows, and coupling points.
Nice-to-Haves
Hands-on experience with AWS Lambda, SQS, SNS, and RDS.
Comfort operating alongside an in-house AI-agent orchestrator that supports and automates parts of our SDLC.
Our Promise: Shieldpay is an equal opportunities employer. For Shieldpay building a fair and transparent workforce begins with the recruitment process that does not discriminate on the grounds of gender, sexual orientation, pregnancy or maternity, gender reassignment, race, colour, nationality, ethnic or national origin, religion or belief, disability or age. We offer flexible working options, such as flexible hours and hybrid work, to support our employees' work-life balance
- Team
- Technology
- Locations
- London
- Remote status
- Hybrid
- Employment type
- Full-time
- Employment level
- Technicians
Workplace & culture
Our team is filled with ambitious, curious and entrepreneurial people. We hire and nurture inquisitive, creative minds looking to flourish in a supportive and collaborative environment, recognised by being placed within the top 100 startups to work for in 2022 by Tempo and Flexa certified in 2023
We don’t like old fashioned corporate hierarchy. Instead we like to empower our people to make a change and be autonomous in their role with all the support you need with the other teams around you.
About Shieldpay
Shieldpay Limited: Regulated by the Financial Conduct Authority under the Payment Services Regulations 2017 (Reference number 770210) as an authorised payments institution. Shieldpay is a company providing simple and transparent payment solutions across the legal, financial, and professional services industries. The firm offers Third-Party Managed Accounts, Escrow facilities and payment agent services.
Shieldpay Trust Services Limited: Registered with HMRC as a trust service provider (Reference XKML00000214627) and provides the services as a corporate trustee to the beneficiaries of the trust, established by deed, in connection with escrow transactions.
Registered Address for our Group Companies is 3rd Floor, 1 Ashley Road, Altrincham, Cheshire, WA14 2DT.