Principal Software Engineer

Principal Engineer

London | Hybrid | Permanent

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
• Design and evolve low-latency, event-driven distributed systems
• 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
• Proven experience building scalable, high-performance distributed systems
• 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

Benefits:

• 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.