Highly Advanced .NET Developer / Architect

Upwork Job Post: Highly Advanced .NET Developer / Architect Job Title Senior / Advanced .NET Developer Needed for Complex Web Applications, APIs, Integrations & Enterprise Systems Job Overview We are looking for a highly advanced .NET developer who can work on complex, production-grade applications involving backend architecture, APIs, integrations, databases, performance optimization, and enterprise-level workflows. This is not a basic development role. We need someone who can think like an architect, write clean and scalable code, debug complex issues, and work independently with minimal hand-holding. The ideal candidate has deep experience with C#, ASP.NET Core, .NET Framework / .NET 6+, SQL Server, Entity Framework, REST APIs, third-party integrations, authentication, cloud infrastructure, and enterprise application architecture. You should be comfortable working on both new builds and legacy systems, including refactoring, performance tuning, troubleshooting, and building scalable backend services. Responsibilities You may be responsible for: Building and maintaining advanced .NET applications using C#, ASP.NET Core, and/or .NET Framework Designing scalable backend architecture and clean application patterns Developing REST APIs and integrating with third-party systems Working with SQL Server, stored procedures, Entity Framework, and database optimization Debugging complex production issues Refactoring legacy code and improving system performance Implementing authentication, authorization, and secure API patterns Supporting integrations with platforms such as ERP, CRM, e-commerce, OMS, payment gateways, shipping systems, or other enterprise tools Reviewing code and recommending architecture improvements Writing clean, maintainable, well-documented code Collaborating with project managers, QA, frontend developers, and technical leadership Required Experience You should have strong professional experience with: C# ASP.NET Core .NET Framework and modern .NET versions REST API development SQL Server Entity Framework / EF Core LINQ Dependency Injection Authentication / Authorization Git Debugging and performance optimization Enterprise application development Clean architecture, design patterns, and scalable code structure Strong Plus Experience with any of the following is a major plus: Azure or AWS Microservices architecture Docker / containerization CI/CD pipelines RabbitMQ, Azure Service Bus, Kafka, or other queueing systems E-commerce integrations ERP / CRM / OMS integrations Payment gateway integrations Background jobs, scheduled tasks, and worker services Multi-tenant SaaS platforms Legacy .NET modernization Angular, React, or Blazor Ideal Candidate The right person for this role is: Senior-level and highly technical Able to explain technical decisions clearly Comfortable auditing existing codebases Strong at debugging difficult issues Able to work independently Detail-oriented and reliable Honest about risks, estimates, and blockers Comfortable joining calls when needed Able to document their work clearly Engagement Type This is a remote contractor role. We are open to either part-time or full-time depending on fit, availability, and project needs. Please include examples of advanced .NET projects you have worked on, especially anything involving complex backend logic, enterprise integrations, API development, or performance optimization.