Overview
We are looking for a Senior .NET Developer to join a critical payments resilience programme on a contractual basis. The successful contractor will engage closely with teams in Architecture, Security, Cloud/DevOps, and QA to design and build a new Azure-hosted payment capability, focusing on creating robust, scalable solutions. This role is suitable for those with deep expertise in .NET and a proven track record in high-volume transaction processing environments.
Responsibilities
- Architect, build, and deploy new transactional APIs and resilient worker services using modern C# and ASP.NET Core.
- Engineer robust resilience mechanisms, including idempotency keys, duplicate-payment prevention, automated retries, circuit breakers, and dead-letter handling.
- Build backend workflows for end-of-day and real-time transaction reconciliation with external payment gateways and banking networks.
- Implement strict security best practices, configuring OAuth 2.0 / OpenID Connect, JWT validation, Azure Key Vault, and Managed Identities.
- Containerize services using Docker and target modern hosting infrastructure (Azure Container Apps / AKS).
- Configure observability, tracing, and operational alerting across transactional boundaries using Azure Application Insights and OpenTelemetry.
- Maintain rigorous test coverage through comprehensive unit, integration, and contract testing.
Requirements
- Deep expertise in modern C# / ASP.NET Core, asynchronous programming, clean DI patterns, and SOLID engineering fundamentals.
- Proven track record with transactional systems: distributed state, concurrency, idempotency, retry policies, and fault recovery.
- Advanced skills in Entity Framework Core and SQL Server / Azure SQL, including schema design and index optimization.
- Hands-on experience with Docker/containerized microservices and Azure services such as Azure Container Apps and Azure Key Vault.
- Solid understanding of OAuth 2.0, OpenID Connect, and token-based API security.
- Practical experience writing effective unit and integration tests within automated CI/CD pipelines.
- Direct domain experience in Payments, Fintech, Core Banking, or high-volume transaction processing is highly desirable.