Senior Software Engineer

Harrington Starr; Greater London; On-site; GBP 80,000 - 110,000; Full time

Benefits offered by this job

Hybrid working model

Job summary

Harrington Starr is seeking an experienced Software Engineer to join a scaling fintech. You will develop and enhance core trading and treasury systems, building new features and improving performance within a high-performing team.

You will work on complex, high-impact systems handling large-scale transactions, with hybrid working flexibility and a culture of collaboration and growth.

Qualifications

• 5+ years of experience with C#.NET in commercial software.
• Experience developing middle and back-office systems.
• Hands-on with cloud-native solutions (Azure or AWS).
• Knowledge of event-driven, microservices architectures.
• Full SDLC experience from design to delivery and support.

Responsibilities

• Develop and maintain the full-stack software across the trading and treasury domain.
• Contribute to architecture and design decisions.
• Support, optimise and maintain production code.
• Research and integrate new technologies.
• Foster engineering excellence and continuous improvement.

Skills

C#/.NET

Back/middle office

Cloud-native

Event-driven/microservices

Full SDLC

AI technologies

Job description

Harrington Starr has partnered with a fast-growing fintech that’s transforming how businesses manage foreign exchange and treasury operations. Their technology enables clients to access institutional-grade execution, automate manual workflows, and gain greater transparency across their financial processes. Handling billions in transactions each year, they continue to expand their product offering and deliver cutting-edge solutions that help clients manage risk more effectively.

The Role

This is an excellent opportunity for an experienced Software Engineer — ideally with a background in financial technology or FX — to join a high-performing engineering team within a scaling fintech. You’ll be instrumental in developing and enhancing the company’s core trading and treasury systems, building new features, improving performance, and driving integration across their technology stack.

Key Responsibilities

• Develop and maintain software across the full stack
• Contribute to architecture and design decisions
• Support, optimise, and maintain production code
• Research and integrate new technologies
• Foster a culture of engineering excellence and continuous improvement

Key Requirements

• 5+ years’ experience working with C#/.NET
• Experience developing middle and back office systems
• Experience with cloud-native solutions (Azure or AWS)
• Knowledge of event-driven, microservices architectures
• Full SDLC experience — from design through delivery and support
• Interest and utilisation of AI technologies
• Join a fast-scaling fintech building next-generation financial technology
• Work on complex, high-impact systems handling large-scale transactions
• Collaborative, innovative, and growth-oriented team culture
• Hybrid working model with flexibility and autonomy