Principal Software Engineer

Harrington Starr; Greater London; Hybrid; GBP 110,000 - 140,000; Full time

Benefits offered by this job

Hybrid and flexible working

Private Medical Insurance

Life Insurance

Pension

Employee Assistance Programme

25 days annual leave

Bank holidays

Discretionary bonus

Job summary

Harrington Starr is seeking a Principal C# Software Engineer in London to lead real-time trading technology initiatives, modernise platforms and drive architectural re-architecture. The role blends hands-on engineering with leadership and mentoring.

You will shape roadmaps, scale systems, and champion best practices while working in a hybrid model with competitive compensation.

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, ideally across 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 architecture

Modernisation/ migration leadership

Cloud-native architectures / APIs / CI

Financial markets experience

Tools

CI/CD tooling

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.