This position is listed on behalf of a partner company, who manages all applications and next steps. Our partner is looking for a .NET Developer based in United States. This is a senior, hands-on development role focused on building, modernizing, and operating a high-availability enterprise application in a secure cloud environment. You will take technical ownership of a complex production codebase supporting a cloud-native microservices architecture and high-volume message processing. The role combines software development, architecture, production troubleshooting, DevSecOps, and technical leadership across the full application stack. You will work extensively with modern .NET, C#, REST APIs, PostgreSQL, messaging technologies, Docker, Kubernetes, and AWS GovCloud. You will also contribute to the responsible adoption of AI-assisted development tools, AI agents, and machine learning capabilities within production systems. Working closely with technical leads, engineering, and operations teams, you will help ensure solutions are secure, scalable, resilient, observable, and maintainable. This opportunity is well suited to an experienced engineer who enjoys solving complex production challenges and influencing engineering standards in a mission-critical environment.