Senior C#/.NET Engineer

Codeworks IT Careers; Westford (MA); On-site; USD 103,320 - 117,096; Full time

Benefits offered by this job

Opportunities for conversion to full-time

Benefits plan eligibility for full-time employees

Job summary

A leading tech company in Westford is seeking a hands-on Senior C#/.NET Engineer to modernize their security integration platform. The ideal candidate will have over 7 years of experience in software engineering, focusing on multi-threaded and event-driven architectures. Responsibilities include designing high-performance services and optimizing backend systems. The anticipated pay is $75-$85 per hour, and the role is onsite three days a week. Join us to be part of an innovative and inclusive workplace.

Qualifications

• 7+ years professional software engineering experience with large, existing codebases.
• Expert C# with .NET Framework/.NET Core and advanced debugging skills.
• Deep experience in multi-threaded programming and concurrency patterns.

Responsibilities

• Design, implement, and optimize high-performance C#/.NET services.
• Tackle multi-threading and cross-process communications.
• Lead modernization efforts and ensure low latency.

Skills

Multi-threaded programming

Event-driven architectures

C#/.NET proficiency

Problem solving

System programming

Tools

SQL Server

Entity Framework

REST APIs

Job description

About Codeworks

Codeworks, an LRS Company, has over 25 years of experience serving Fortune 500-1000 companies in Wisconsin as well as our client's national locations. Our recruiting team excels at evaluating, advising, and connecting IT professionals with new opportunities that will satisfy their expectations regarding income and opportunity for growth. At Codeworks, we're committed to diversity, equity, and inclusion in our workforce and beyond. We believe in equal opportunities and value the unique perspectives that every individual brings to our team. Join us in creating an inclusive, innovative, and collaborative workplace where your talents can thrive.

Location: Westford, MA (Onsite T/W/Th; no relocation — local candidates only)

Type: Contract with high intent to convert

Work Authorization: W2 only (no C2C). Must be authorized to work in the U.S. now and in the future; sponsorship not available.

Who We're Looking For

We’re seeking a hands-on Sr. C#/.NET Engineer to accelerate modernization of our client's security integration platform, a long-lived, mission-critical system that supports 1,000+ IoT clients and devices globally. You’ll work deep in the server platform (not UI/web), tackling multi-threaded, event-driven, cross-process communication at scale, improving stability and performance, and guiding architectural evolution (e.g., moving from singleton services to active-active).

This role is not a fit for predominantly UI/Web/ASP.NET profiles or engineers who haven’t built/owned multithreaded server architectures. (You may be able to write apps/UI, but the core need is backend/server concurrency and real-time systems.)

If you thrive in complex, high-uptime systems and can ramp quickly in a large codebase, you’ll feel right at home here.

Responsibilities

• Serve as a principal-level contributor within a small, senior team (<10), partnering with architects and a new manager to augment delivery capacity.
• Design, implement, and optimize high‑performance C#/.NET services and integration components for a distributed, event-driven platform.
• Tackle multi-threading, cross-process communications (IPC), and Windows services/system-level programming to ensure low latency and resilience.
• Diagnose and resolve complex defects, performance bottlenecks, and reliability issues across a 15-year production system.
• Lead/drive modernization: refactoring legacy components, evolving architecture, and enabling active-active operations for multiple services.
• Build real-time capabilities powering live security system status and analytics within the application.
• Mentor engineers, promote engineering best practices, and uphold cybersecurity principles.

Qualifications

• 7+ years professional software engineering experience with large, existing codebases.
• Expert C# with .NET Framework/.NET Core and advanced debugging.
• Deep experience with:
  • Multi-threaded programming and concurrency patterns
  • Event-driven/message-based architectures
  • Windows services and system-level programming
  • Networking protocols, sockets, real-time communications
  • Cross-process communications (IPC), e.g., sockets, named pipes, shared memory
  • Proven delivery of highly reliable, fault-tolerant backend services.
• Strong problem solving and crisp written documentation skills.
• Comfortable operating independently with minimal ramp time in a contract-to-convert setting.

Preferred Qualifications

• Domain exposure to access control/security integrations or similar real-time device/customer integration systems (helpful but not required).
• Experience with:
  • SQL Server, ADO.NET, Entity Framework, stored procedures
  • Diagnostic tooling, memory profiling, performance analysis; Windows memory dump analysis
  • REST, SOAP, or custom protocol integrations
  • Copilot AI familiarity (nice-to-have for coding efficiency; not required).

Codeworks discloses that the anticipated hourly pay range for this position is between $75 and $85. This range is subject to change based on job‑related factors, including client requirements where applicable. All full‑time Codeworks employees are eligible to enroll in the company’s benefits plan.

Codeworks, an LRS Company, is an equal opportunity employer. Applicants for employment will receive consideration without unlawful discrimination based on race, color, religion, creed, national origin, sex, age, disability, marital status, gender identity, domestic partner status, sexual orientation, genetic information, citizenship status or protected veteran status.

In some cases, LRS Consulting uses generative artificial intelligence (“AI”) in support of our hiring processes. LRS takes steps to ensure the use of AI does not result in discrimination based on protected class(es). AI may be used in the hiring process solely in support of the assessment of candidate qualifications. All decisions in the hiring process are made by LRS employees. If AI will be used in the hiring process for the position for which you are applying, you will be notified and will have the opportunity to opt out. Please contact [e-mail] with any questions.