Software Engineer C#

The Opportunity

I am exclusively headhunting for a hyper-growth, venture-backed fintech startup that is completely disrupting the cross-border digital treasury and real-time FX landscape. They deploy an AI-powered, real-time capital connectivity platform to multinational corporate treasuries, while white-labeling their infrastructure directly to giant global banks.

Following massive revenue growth, we are doubling the London engineering team. This is a pure greenfield engineering environment with zero corporate bureaucracy and high-stakes technical complexity.

The Role

I am looking for a heavy-hitting, backend-focused C# / .NET Software Engineer to take absolute ownership of core transaction infrastructure, multi-bank API connectors, and real-time event-driven pipelines.

You will be embedding AI automation into financial workflows, building agentic LLM pipelines for automated data classification, and engineering low-latency transaction normalization engines where millions of pounds in cross-border liquidity are processed under high concurrent load.

Core Responsibilities:

• Distributed Architecture: Design and build horizontally scalable microservices and real-time API integrations connecting to global banking rails.
• AI & Automation: Integrate advanced AI/LLM tooling (e.g., Claude Code, OpenAI API) to build intelligent data classification and automated workflow engines.
• High-Concurrency Engineering: Solve complex data correctness challenges, handling multi-bank event streams, exactly-once processing, and retry-backed message pipelines.
• Greenfield Delivery: Write clean, high-performance .NET 8/9 code, driving features from architectural conception to live production.

What We Are Looking For:

• The Tech Stack: Deep, production-grade mastery of C# and modern .NET Core / .NET 8+, SQL, and familiarity with AI integration.
• Domain Experience: A proven track record handling complex data streams—ideally within Fintech, FX, Payments, Front-Office Trading, or low-latency infrastructure.
• Architectural Fluency: Event-driven architecture, asynchronous messaging (RabbitMQ/Service Bus), and caching (Redis).
• The Startup Mindset: High technical autonomy and a passion for engineering craftsmanship using modern tools.