## Job Description# Senior .NET Developer – Modernization Lead* Lead architectural design, development, and modernization efforts across enterprise C#/.NET applications.* Provide technical ownership for modernization initiatives including legacy refactoring, cloud‑readiness, and system resiliency.* Translate complex business requirements into scalable, secure technical solutions in collaboration with Business Analysts and Product Owners.* Establish and enforce architectural standards, coding practices, and design patterns.* Reduce technical debt and systemic risk through structured remediation plans.* Coordinate cross‑team technical efforts where integrations overlap.* Mentor developers through design reviews, code reviews, and modernization best practices.* Design, implement, and govern secure, scalable RESTful APIs and backend services.* Lead root‑cause analysis of high‑complexity production issues and implement durable fixes.* Collaborate with QA and DevOps to strengthen automation, release quality, observability, and deployment reliability.* Contribute to operational readiness planning, monitoring strategies, and production stability improvements.* Identify and proactively mitigate architectural risks throughout the delivery lifecycle.* Bachelor’s degree in Computer Science, Information Systems, Engineering, or equivalent experience.* 7+ years building enterprise applications using C# and .NET (Framework and .NET Core/8/9+ preferred).* Demonstrated experience leading architectural decision‑making within complex or legacy environments.* Strong expertise in ASP.NET MVC and API‑driven architectures.* Advanced Microsoft SQL Server experience (performance tuning, indexing, query optimization).* Proven success modernizing legacy systems, refactoring monolithic architectures, and improving maintainability.* Expertise in secure RESTful API design (JWT, OAuth, claims‑based security).* Experience implementing structured logging, monitoring, and observability in production.* Strong understanding of dependency injection, middleware, async/await, background services, and distributed processing.* Working knowledge of modern SPA frameworks (Angular or React).* Experience mentoring developers and influencing technical standards in Agile environments.* Proficiency with Git‑based source control and CI/CD automation.* Demonstrated ability to identify systemic risk and create durable, maintainable architecture solutions.* Experience working in matrixed, cross‑agency, or public‑sector environments.* Experience using LLMs and automation tools to enhance engineering productivity.* Familiarity with cloud platforms and cloud‑native architectures.* Demonstrable senior‑level experience modernizing .NET systems (Core/6+/Cloud).* Proven ownership, autonomy, and accountability for delivery outcomes.* Advanced SQL Server performance tuning skills (indexing, execution plans, deadlock analysis).* Experience with regulated environments (HIPAA, CJIS, FERPA, SOC2) preferred.* Ability to lead technical design and mentor junior developers.* Resumes must be kept to 2 pages maximum.*Apex Systems is a world-class IT services company that serves thousands of clients across the globe. When you join Apex, you become part of a team that values innovation, collaboration, and continuous learning. We offer quality career resources, training, certifications, development opportunities, and a comprehensive benefits package. Our commitment to excellence is reflected in many awards, including ClearlyRated’s Best of Staffing in Talent Satisfaction in the United States and Great Place to Work in the United Kingdom and Mexico. Apex uses a virtual recruiter as part of the application process. Click* *for more details.*
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