Principal Software Engineer at CipherTek Recruitment, City Of London, £750 per day

Principal Software Engineer – Testing Architecture & Engineering Quality

📍 London (1 day/week) | 💰 £750/day Outside IR35 (Flexible) | 📅 12-Month Initial Contract

Shape the Future of Engineering Quality at a Leading Investment Bank

A leading investment bank is looking for an exceptional Principal Software Engineer to define and build the future testing architecture across its strategic Global Markets Front Office trading platform.

This is a highly technical Principal Software Engineering position - not a QA, Test Analyst or traditional SDET role.

The successful candidate will join a team with an exceptionally high technical bar. We're looking for someone who thinks like an architect, writes production-quality code, and enjoys solving complex engineering problems through frameworks, tooling and platform design rather than feature development alone.

You'll define the engineering foundations that underpin software quality across the organisation - designing reusable frameworks, shared libraries, AI-assisted developer tooling and architectural patterns that improve quality, resilience and developer productivity across a large distributed platform.

What You'll Be Doing

• Define the testing and engineering quality architecture across a strategic Front Office trading platform.
• Design and build reusable frameworks, libraries and shared engineering tooling.
• Develop framework-level code across .NET/C#, Python and TypeScript.
• Design engineering patterns that operate consistently across multiple runtimes.
• Build AI-powered tooling that improves developer productivity and automates engineering quality.
• Design contract testing and containerised testing solutions for distributed services.
• Integrate tooling into an NX Monorepo and CI/CD pipelines.
• Partner with senior engineers and architects to improve engineering quality across Global Markets.
• Remain highly hands-on while influencing the long-term technical direction of the platform.

What We're Looking For

We're looking for an exceptional software engineer, not simply someone with testing experience.

You'll likely have a background as a Principal Engineer, Staff Engineer, Platform Engineer, Software Architect or a highly technical SDET operating at architecture level.

You should demonstrate:

• Outstanding software engineering ability with experience building complex backend or distributed systems.
• Expert-level commercial experience with C# (.NET) and/or Python.
• Experience designing frameworks, shared libraries, developer tooling or platform capabilities.
• Strong software architecture skills and an ability to design scalable, maintainable engineering solutions.
• A polyglot mindset with experience working across multiple technology stacks.
• A passion for improving engineering quality through architecture, automation and developer tooling.
• Experience integrating tooling into CI/CD pipelines and large shared codebases.
• Excellent communication skills with the ability to influence senior technical stakeholders.

Highly Desirable

• AI-assisted engineering or developer tooling.
• Contract testing.
• Testcontainers or containerised testing.
• NX Monorepo.
• TypeScript.
• Playwright or Cypress.
• Front Office / Global Markets experience.

This Role Probably Isn't For You If...

• Your experience is primarily manual testing or test execution.
• You've mainly focused on building automated test suites rather than engineering platforms, frameworks or developer tooling.
• You're looking for a traditional QA or frontend automation role.
• Your background is primarily feature development without experience designing engineering architecture or platform capabilities.

Why Join?

✔ Outside IR35 contract

✔ 12-month initial engagement with long-term potential

✔ 1 day per week in the London office

✔ Strategic Front Office Global Markets platform

✔ Opportunity to define engineering quality across an enterprise-scale technology estate

✔ Highly technical, hands-on architecture role with significant influence over engineering standards

If you're a technically exceptional engineer who enjoys solving engineering quality challenges through architecture, frameworks and platform design, we'd love to hear from you.