Senior .NET Engineer

Impact and Responsibilities

We're a small engineering team behind a regulated payments platform that holds, verifies and disburses client money. We're looking for a Senior .NET Engineer to help shape where it goes next: building what our customers need, making our core safe to change, and bringing it onto modern .NET step by step rather than rewriting it. You'll work across the whole platform, with a real say in its direction.

Build for our customers

• Deliver features and improvements for the firms that use Shieldpay, from making the platform self-service end to end to enterprise needs such as single sign-on.

• Build new services cleanly, with dependency injection, robust authentication and authorisation, structured logging and full observability.

Make our core safe to change, and modernise it

• Extract business rules from undocumented SQL Server stored procedures and C# into clean, tested rules assemblies. They target netstandard2.0, so they run inside our .NET Framework platform today and on modern .NET tomorrow.

• Work across the links between our two platforms: an API façade, a database proxy and SNS/SQS events. Neither platform stands alone, and most real bugs live in the coupling, not on one side.

• Ship changes in shadow mode: compute, log and compare against the legacy outcome without writing, until equivalence is demonstrated.

Shape how we build

• Help set the platform's technical direction. Our target shape is a starting point to be tested, and the team changes it where the evidence says it's wrong.

• Build with AI properly: the test harness in place first, and the gains measured, not assumed.

• Take the lead on an area of the platform: own it end to end, set its technical direction and lead the work day to day.

What we're looking for in you

• You're senior and hands-on in modern .NET, as well as deeply comfortable in legacy .NET Framework 4.x (ASP.NET MVC 5, Web API 2, Entity Framework 6). You respect legacy code and are happy working in it today.

• You read, understand and safely change complex SQL Server logic.

• You're comfortable working in JavaScript/TypeScript: jQuery on the legacy front end, and TypeScript services on our sister platform.

• You have a "boring technology" instinct. You favour stability, predictability and incremental progress over rewriting everything or chasing trends.

• You've proved equivalence before, using golden-master testing, diffing or shadow verification to show that new code matches legacy outputs.

• You can hold two architectures in your head at once, and reason through their edge cases, data flows and coupling points.

How you work

• You ask before you design. When a problem is underspecified, you draw out who it's for, how many, what can fail and what's regulated before proposing anything.

• You're correct by default. You raise idempotency, partial failure, audit trails and reconciliation without being prompted.

• You choose the simplest thing that works, and steer others away from over-engineering.

• You push back with reasons, and change course when you're shown something new.

• You turn large, ambiguous problems into work the team can pick up, and keep it moving.

• You make the people around you better through reviews, pairing and mentoring, and you hold AI-generated work, yours and theirs, to the same standard as anything else.

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