Principal Software Engineer

Harrington Starr; Greater London; Hybrid; GBP 126,000 - 154,000; Full time

Benefits offered by this job

Private Medical Insurance

Life Insurance

Pension

Employee Assistance Programme

Job summary

Harrington Starr in London is seeking a Principal C# Software Engineer to shape architecture for real-time trading technology and lead a strategic re-architecture programme. This senior role blends hands-on engineering with architecture, mentoring, and collaboration across teams to deliver robust, scalable platforms.

You will drive platform modernisation, oversee production readiness, and push for improvements in CI/CD, observability and performance while guiding engineers and partners in

Qualifications

• Strong C#/.NET software engineering experience.
• Strong understanding of real-time and low-latency architecture.
• Experience leading modernisation, migration or re-architecture programmes.
• Experience with cloud-native architectures, APIs, event-driven systems and CI/CD.
• Financial markets experience with electronic trading, OTC derivatives, fixed income, FX or similar.

Responsibilities

• Shape the technical roadmap and platform re-architecture strategy.
• Lead platform development through to production and improve scalability, resilience and performance.
• Drive improvements across automation, observability, CI/CD and developer productivity.
• Partner with Engineering, Product and Operations to deliver practical technical solutions.
• Mentor engineers and champion engineering standards, best practices and continuous improvement.

Skills

C# / .NET

Real-time / Low-latency

Technical leadership

CI/CD

Job description

Salary: Up to £140,000 + Bonus & Benefits

Harrington Starr is partnering with a leading financial technology firm to hire a Principal C# Software Engineer based in London.

This is a senior technical leadership role focused on real-time trading technology, platform modernisation and re-architecture, combining hands‑on engineering, architecture and mentoring.

The Role:

• Shape the technical roadmap and platform re-architecture strategy
• Lead platform development through to production and improve scalability, resilience and performance
• Drive improvements across automation, observability, CI/CD and developer productivity
• Partner with Engineering, Product and Operations to deliver practical technical solutions
• Mentor engineers and champion engineering standards, best practices and continuous improvement

What We're Looking For:

• Strong C#/.NET software engineering experience
• Strong understanding of real-time and low-latency architecture
• Experience leading modernisation, migration or re-architecture programmes
• Experience with cloud-native architectures, APIs, event-driven systems and CI/CD
• Financial markets experience, ideally across electronic trading, OTC derivatives, fixed income, FX or similar, with strong technical leadership skills
• Up to £140,000 base salary + discretionary bonus
• 25 days annual leave + bank holidays
• Hybrid and flexible working
• Private Medical Insurance and Life Insurance
• Pension and Employee Assistance Programme

If you’re a Principal-level C# engineer looking to shape architecture, modernise complex platforms and work on real‑time financial technology, we’d love to hear from you.