Principal C#/.NET Engineer

We are seeking a seasoned Sr. Principal C#/.NET Engineer to lead the modernization and enhancement of a large-scale, mission-critical security integration platform. This is a high-impact technical role for a “heavy hitter” who thrives on solving deep architectural challenges and debugging complex, distributed systems. You will be responsible for accelerating the delivery of high-priority features while ensuring the platform remains highly reliable and fault-tolerant. The ideal candidate can jump into a massive, existing codebase and become productive almost immediately., Core Platform Engineering: Design, implement, and optimize high-performance C# services and frameworks for a large-scale security ecosystem. Architectural Modernization: Lead refactoring efforts and architectural improvements to modernize legacy components while maintaining system integrity. Complex Problem Solving: Troubleshoot and resolve deep-level bugs, memory bottlenecks, and reliability issues across multi-threaded and event-driven systems. Distributed Patterns: Work extensively with message-based architectures, Windows services, and real-time communication protocols (Sockets, Networking). Technical Documentation: Author clear technical documentation for complex APIs, system interfaces, and deployment processes to ensure long-term maintainability. Mentorship: Serve as a technical authority within the engineering team, providing guidance and mentorship to mid-level and senior engineers.

Education: Bachelor’s or Master’s in Computer Science or a related technical field. Experience: 7-10 years of professional software engineering with a focus on backend systems. Technical Mastery: Expert-level C#: Deep knowledge of the .NET ecosystem (Framework and Core). System Internals: Strong experience in multi-threaded programming and Windows system-level services. Real-Time Communications: Proficiency in networking protocols, sockets, and message-based architectures. AI Integration: Experience leveraging Copilot AI and various LLM models to accelerate development. Attributes: Proven ability to work independently in a contract environment with minimal ramp-up time and a “solution-first” mindset.

Preferred Credentials Prior experience with Security Integration or Access Control platforms. Advanced diagnostic skills: Windows Memory Dump analysis, memory profiling, and performance tuning. Database expertise: SQL Server, ADO.NET, and Entity Framework. Modern DevOps fluency: Azure DevOps, GitHub Actions, and CI/CD pipeline management. Equal Opportunity Employer / Disabled / Protected Veterans

For temporary assignments lasting 13 weeks or longer, AllSTEM Connections is pleased to offer major medical, dental, vision, 401k and any statutory sick pay where required.

We are committed to working with and providing reasonable accommodations to individuals with disabilities. If you need a reasonable accommodation for any part of the employment process, please contact your staffing representative who will reach out to our HR team.

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We also consider for employment qualified applicants regardless of criminal histories, consistent with legal requirements, including, if applicable, the City of Los Angeles’ Fair Chance Initiative for Hiring Ordinance. Pursuant to applicable state and municipal Fair Chance Laws and Ordinances, we will consider for employment-qualified applicants with arrest and conviction records, including, if applicable, the San Francisco Fair Chance Ordinance. For Los Angeles, CA applicants: Qualified applications with arrest or conviction records will be considered for employment in accordance with the Los Angeles County Fair Chance Ordinance for Employers and the California Fair Chance Act.