Senior .NET Developer (Platform Modernization & Support)

Overview

We are actively modernizing a legacy software platform and are seeking a highly experienced, self-directed .NET Developer to support this effort. The current system is primarily built in Classic ASP and .NET Framework 4.6. We are looking for someone who can quickly assess the current state of the system, understand how it works, and take ownership of the .NET portion of code. You’ll work closely with an experienced Classic ASP developer, the Chief Product Officer, and the Director of Customer Success to support customers while steadily advancing the platform.

Key Responsibilities

• Support customer issues and production tickets related to the .NET components of the platform
• Rapidly assess and understand existing code and system behavior with minimal ramp-up time
• Take ownership of the .NET portions of the system and drive improvements
• Recommend and implement modernization approaches, including refactoring, restructuring, and incremental architecture improvements
• Apply best practices for code quality, maintainability, and performance
• Contribute to ongoing modernization by designing and building improved .NET-based components
• Collaborate with the Classic ASP developer on cross-system issues
• Work closely with the Chief Product Officer and Director of Customer Success to align technical work with product priorities
• Participate in planning, prioritization, and lightweight release cycles

Required Qualifications

• 5+ years of professional .NET development experience with C# as the primary language
• Demonstrable experience inheriting and working within large, partially undocumented legacy codebases
• Direct SQL Server experience — querying, stored procedures, performance analysis, and schema navigation
• Experience maintaining or modernizing IIS-hosted applications in a Windows Server environment
• Ability to read and reason through Classic ASP / VBScript code for cross-system debugging (you do not need to write it)
• Strong REST API design and implementation experience with ASP.NET Core
• Self-directed — able to assess a system independently and determine the right next step without being told
• Hands-on executor — this role requires implementation, not just architectural guidance or recommendations

Nice to Have

• Experience with health informatics, public health IT, or government-regulated platforms
• Familiarity with HL7 v2.x messaging and immunization information systems (IIS)
• Experience establishing CI/CD pipelines from scratch on legacy .NET projects
• Background introducing automated testing to previously untested codebases
• Experience with AI-assisted development workflows and comfort directing LLMs to produce production-quality code
• Familiarity with PostgreSQL and cross-database data synchronization patterns
• HIPAA / PHI data handling experience
• Strong debugging and problem-solving skills in live production environments
• Ability to work independently and deliver value with minimal direction

Technology Landscape

• C#, ASP.NET, Classic ASP, .NET Framework 4.x, .NET Core / .NET 6+
• Classic ASP, Javascript, Jscript
• Microsoft IIS 10, Windows Server 2019
• ASP.NET Core Identity / JWT, HTTPS / TLS on IIS, CSP Headers, CSRF / Cookie Policy, Windows Authentication
• Visual Studio 2022, Atlassian Jira / Bitbucket

Engagement Details

• Part-time contract (~10 hours per week)
• Flexible schedule
• Long-term engagement with ongoing investment in platform modernization

What We’re Looking For

A highly experienced .NET developer who can quickly assess a system, determine the right path forward, and implement meaningful improvements — someone who brings both strong technical judgment and hands-on execution.

Pay: $60.00 - $85.00 per hour

Expected hours: 8.0 – 12.0 per week

Work Location: Remote