C# .NET Engineer — 3-5 Month Contract (Refactoring + New Features)

We are seeking an experienced C# .NET Engineer for a 3-5 month engagement to help refactor existing code and deliver new functionality in a modern, contract-driven API architecture.

This role is for a senior-level engineer who understands how to build predictable, maintainable APIs, not just write code. You should be confident working independently, identifying design flaws, and applying architectural improvements with precision.

🔧 Responsibilities

• Refactor and improve existing .NET APIs to align with architectural and design standards
• Develop new functionality across core services
• Ensure all endpoints return standardised ApiResult wrappers (Result, ValidationApiResult)
• Maintain consistent error handling via application/problem+json (RFC 7807)
• Work within a contract-driven architecture using Scalr for contract enforcement and contract testing
• Implement fully async end-to-end patterns (Task)
• Ensure all APIs inherit consistent error handling from base classes
• Optimise Entity Framework usage including query design, performance tuning, and relationships
• Write clean, modular, and testable code that reflects engineering discipline

✅ Required Skills and Experience

• 5 plus years professional experience with C# and .NET, Core or 8 preferred
• Deep hands-on expertise with Entity Framework Core
• Proven experience with async and await and Task-based APIs
• Strong understanding of RESTful API design and HTTP standards
• Familiarity with RFC 7807 for structured error responses
• Experience using Scalr for API contract validation and enforcement
• Knowledge of contract testing principles
• Excellent debugging, analytical, and problem-solving skills

💡 Nice to Have

• Experience with CSharpFunctionalExtensions
• Familiarity with FluentValidation
• Exposure to Azure App Services, Application Insights, or other cloud monitoring tools
• Experience in environments using functional result wrappers and strict API governance

📅 Duration

• 3-5 months initially, with the possibility of extension based on performance and roadmap priorities

🌏 Location and Hours

• Ukraine-based candidates are strongly preferred
• Must have excellent English communication
• Must be available for our daily standup with the Australian team at 7:45 am Ukraine local time, which is 4:45 am Sydney time

🧠 About the Project

• You will join a product team focused on building an enterprise-grade API platform built around contract governance, functional result wrappers, and predictable API conventions. We value engineers who care deeply about architecture, code quality, and observability, not just output.