Principal Software Engineer

Company: Harrington Starr
Apply for the Principal Software Engineer
Location: London
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.

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Posted: September 22nd, 2026