Sr C# Developer

**This position is listed on behalf of a partner company, who manages all applications and next steps. Our partner is looking for a Sr C# Developer based in the United States.** This is a senior engineering opportunity focused on modernizing production Java microservices by migrating them to C# and .NET. You’ll combine deep Java expertise with strong C#/.NET experience to translate existing services into the client’s established architecture, patterns, and conventions. AI-assisted conversion will provide an initial foundation, but your expertise will be critical in reviewing, correcting, testing, and completing the resulting code. You’ll be responsible for preserving functional behavior across APIs, messaging, error handling, logging, configuration, and service contracts. The role goes beyond code conversion, requiring sound engineering judgment to identify edge cases, behavior drift, and situations where direct translation is not appropriate. You’ll collaborate directly with client engineers and help establish reusable patterns, prompts, and quality checks that can scale the migration across multiple services. This is a high-impact contract engagement suited to an experienced developer who enjoys complex modernization work and practical, AI-assisted engineering. ### Accountabilities: - Lead the migration of production Java microservices to C#/.NET, using AI-generated conversion drafts as a starting point and completing the implementation manually according to established C# patterns and coding conventions. - Review AI-generated code critically for correctness, incomplete logic, hallucinated APIs, missed edge cases, security or reliability concerns, and behavioral differences from the original Java implementation. - Translate Java frameworks, language constructs, libraries, and development patterns into appropriate .NET equivalents, including Spring to Core, Maven/Gradle to NuGet, and JPA/Hibernate to Entity Framework. - Preserve existing service contracts and production behavior, including REST endpoints, message formats, error handling, logging, configuration, and service-to-service interactions. - Develop, adapt, and maintain automated unit and integration tests to demonstrate functional parity between the Java source services and their C#/.NET implementations. - Contribute to the broader migration methodology by developing reusable prompt templates, conversion patterns, pattern libraries, review checklists, and other practices that enable consistent modernization across multiple services. - Collaborate directly with client engineering teams, communicate technical trade-offs clearly, provide constructive feedback, and identify situations where a straightforward code conversion may not be the best technical solution. ### Requirements - 8+ years of professional experience developing production Java applications and microservices, preferably with Spring Boot or a comparable framework, with the ability to understand unfamiliar Java code and explain its underlying behavior and design. - 5+ years of hands-on C# and .NET experience, including .NET Core/.NET 6+, Core Web APIs, dependency injection, asynchronous programming patterns, and production application development. - Demonstrated experience personally performing code migration, re-platforming, modernization, or conversion between programming languages or frameworks rather than simply maintaining an already-migrated codebase. - Strong understanding of microservices architecture, REST APIs, service-to-service communication, containerization with Docker, and CI/CD practices. - Strong automated testing discipline, with the ability to use unit and integration testing to establish functional equivalence rather than relying primarily on manual or visual code inspection. - Ability to work independently in a contract or staff-augmentation environment while communicating effectively with both technical teams and business stakeholders. - Strong analytical and problem-solving skills, with the judgment to distinguish between direct translations and areas that require architectural or behavioral adaptation. - Experience with AI-assisted development tools such as GitHub Copilot, Claude, ChatGPT, or similar platforms for code conversion, refactoring, or software development is highly desirable. - Familiarity with LLM-assisted development workflows, including prompt design, output validation, agentic coding tools, and understanding the limitations and failure modes of AI-generated code, is a strong plus. - Experience with Kubernetes, AWS or Azure, and API gateways such as Kong is beneficial. - Exposure to MySQL, SQL Server, and Python for development or migration tooling is advantageous. ### Benefits - Remote position with preference for candidates based in the United States. - Contract or staff-augmentation engagement, with the duration aligned to the scope and progress of the migration initiative. - Opportunity to work on a substantial modernization effort involving production microservices, cloud technologies, AI-assisted development, and cross-language engineering. - Direct collaboration with experienced engineering teams and meaningful influence over migration quality, architecture, testing, and scalable conversion practices. - Hands-on exposure to modern AI-assisted software development workflows, including automated code conversion and LLM-supported engineering. - Opportunity to help establish reusable engineering patterns and processes that can accelerate future migration work. - Compensation and additional contract benefits are determined by the hiring company and will be discussed during the recruitment process.