Senior Backend .NET Engineer - Platform Modernisation

📍 Location: On‑site 4 days per week / 1 day remote
🕒 Contract: 12‑month rolling contract (full‑time)
💼 Engagement: Contractor

The Role

We are looking for a Senior Backend .NET Engineer to support and modernise a large, business‑critical platform used in a regulated environment.

Key Responsibilities

• Refactor and modernise an existing ASP.NET backend, replacing ASP.NET Boilerplate with standard .NET patterns and components
• Work extensively with C# and modern .NET, applying best practices around performance, reliability, and maintainability
• Design and optimise Entity Framework Core usage, including migrations, transactions, and query performance
• Analyse and improve SQL Server performance, including writing efficient queries and troubleshooting database issues
• Debug and resolve issues in a large, complex legacy codebase
• Collaborate with frontend engineers to maintain stable API contracts for a Vue.js application
• Contribute to and improve CI/CD pipelines (Azure DevOps)
• Apply sound algorithmic and performance reasoning when designing or refactoring solutions
• Work closely with the wider engineering team in a structured, quality‑focused development environment

Mandatory Technical Skills

• Strong C# and modern .NET experience
  • Collections and data structures
  • Asynchronous and parallel programming
  • LINQ
• Strong ASP.NET experience
• Hands‑on Entity Framework Core knowledge
  • Migrations
  • Transactions
  • Writing performant queries
• Proven ability to debug and work effectively in large legacy codebases
• Microsoft SQL Server experience
  • Writing performant SQL
  • Investigating and resolving database issues
• Experience working with CI/CD pipelines (e.g. Azure DevOps)
• Solid theoretical understanding of algorithms and performance
  • Runtime and space complexity
  • Designing efficient, scalable solutions

Strong Plus / Nice to Have

• Previous experience with ASP.NET Boilerplate (ABP) and successful migration away from it
• Basic experience with Vue.js
  • Understanding API contracts
  • OpenAPI / Swagger integration
• Exposure to TypeScript