Senior Dotnet Developer

Halian | Managed Services, Recruitment Agency & Contract Staffing; England; On-site; GBP 70,000 - 100,000; Full time

Job summary

London (Hybrid, 2-3 days per week in the office) Senior .NET Engineer to join a high-performing team powering payments, FX, ledgers and client platforms. Build distributed services in .NET/C# on Azure, focusing on reliability, security and production ownership.

You'll design and operate services end-to-end, drive architecture, mentor peers and push for observability and resilient, scalable patterns in a regulated financial environment.

Qualifications

• Strong commercial experience developing applications with .NET and C#.
• Experience designing, building and operating production services in cloud environments (Azure preferred).
• Deep understanding of distributed and event-driven architectures.
• Security, availability, reliability and observability best practices.
• Experience with monitoring/telemetry tools (Grafana, Application Insights).
• Strong SQL Server skills including schema design and performance tuning.
• Experience with modern ORM frameworks (EF Core).
• Testing mindset for reliable, maintainable software.
• Comfort in regulated environments with change control and auditability.
• Excellent communication and architectural decision-making skills.
• Experience using AI-assisted development tools in real-world delivery.

Responsibilities

• Design, build and operate services using .NET 10 and Azure.
• Own services throughout their lifecycle from architecture to production support.
• Build scalable asynchronous and event-driven systems handling retries and duplicates.
• Collaborate across domains including FX, ledger, payments and compliance.
• Drive security, resilience, observability and operational excellence.
• Mentor engineers through code reviews and design discussions.
• Contribute to a culture of continuous improvement and technical excellence.

Skills

NET/C# development

Azure

Distributed systems

Security and reliability

Observability

CI/CD & production ownership

AI-assisted development tools

Mentoring

Architectural discussions

Communication skills

Tools

Grafana

Application Insights

SQL Server

Entity Framework Core

Job description

London (Hybrid, 2-3 days per week in the office)

Build critical financial infrastructure that moves money at scale

We're looking for a Senior .NET Engineer to join a high-performing engineering team responsible for the systems that power payments, foreign exchange (FX), ledgers, reconciliation, compliance, banking integrations and client-facing platforms.

This is an opportunity to work on a true end-to-end financial platform where engineering quality, reliability and ownership matter. You'll design and build distributed services that handle real-world complexity, from payment processing and FX workflows to integrations with banks and payment schemes.

If you're passionate about building resilient systems, solving complex engineering challenges, and owning services all the way through to production, we'd love to hear from you.

What You'll Be Doing

• Design, build and operate services using .NET 10 and Azure.
• Own services throughout their lifecycle, from architecture and development through to production support.
• Build scalable asynchronous and event-driven systems that remain reliable under failure scenarios, retries and duplicate message delivery.
• Work across a broad range of domains including:
• FX pricing and trading
• Ledger and reconciliation systems
• Banking and payment scheme integrations
• Payment compliance
• Client-facing platforms
• Collaborate closely with engineering teams to define and evolve system architecture.
• Drive best practices in security, resilience, observability and operational excellence.
• Use AI-assisted development tools effectively and pragmatically to improve engineering productivity.
• Mentor and support other engineers through code reviews, design discussions and knowledge sharing.
• Contribute to a culture of continuous improvement and technical excellence.

What We're Looking For

• Strong commercial experience developing applications with .NET and C#.
• Experience designing, building and operating production services in cloud environments (Azure preferred, AWS or GCP also considered).
• Deep understanding of distributed and event-driven architectures.
• Hands-on experience dealing with:
• Idempotency
• Message ordering
• Retries and failure recovery
• Strong understanding of security, availability, reliability and observability principles.
• Experience using monitoring and telemetry tools such as Grafana, Application Insights or similar platforms.
• Strong SQL Server experience, including schema design, performance tuning and query optimisation.
• Experience using modern ORM frameworks, ideally Entity Framework Core.
• A strong testing mindset and understanding of how to build reliable, maintainable software.
• Comfortable working within regulated environments where change control and auditability are important.
• Excellent communication skills and the confidence to contribute to architectural discussions and technical decision-making.
• Practical experience using AI-assisted development tools in real-world software delivery.

Nice to Have

Experience in any of the following areas would be beneficial but is not essential:

• Double-entry ledger systems
• Foreign exchange products and pricing
• Payment compliance
• Banking and payment scheme integrations
• FIX protocol and market connectivity

While domain experience is valuable, we're primarily looking for exceptional engineers with a strong foundation in building robust, scalable systems.

• SQL Server
• Grafana
• Application Insights
• AI-assisted development tools

Why Join?

• End-to-end ownership of the services you build.
• Opportunity to influence architecture and technical direction.
• Exposure to complex, business-critical financial systems.
• Modern engineering practices and technology stack.
• Highly autonomous teams with fast decision-making.
• Collaborative environment focused on quality, reliability and continuous improvement.

If you're excited by solving complex distributed systems challenges and want to play a key role in building critical financial technology, we'd love to hear from you.