Principal Full-Stack .NET Engineer - AI Tools

Paychex is reimagining how businesses manage their workforce by bringing payroll, HR, benefits, and advisory services together into a single connected HCM platform. As Paychex and Paycor come together, we're combining innovative technology, data-driven insights, AI, and human expertise to help organizations work smarter, support their people, and achieve better business outcomes. This is an exciting time to join our team as we continue to invest in innovation, simplify client experiences, and shape the future of work. At Paychex, you'll have the opportunity to grow your career, make a meaningful impact, and be part of something bigger as One Paychex.

As a Principal Software Engineer, you will provide strategic technical partnership across teams building a modern, cloud-native software delivery platform — including a web front end, core service APIs, AI agent-driven automation, and the cloud infrastructure that hosts them. You will drive architecture, design, and delivery of scalable solutions spanning these areas, partner with Product and Engineering to solve complex business challenges, mentor engineers at all levels, and help shape the technical direction of an engineering organization that is increasingly building alongside AI agents rather than just building AI features.

• Lead architecture and design decisions across service boundaries (front end, back-end APIs, automation/agent tooling, infrastructure), including authentication models, data ownership, and integration protocols.
• Drive agentic development practices  across a modern AI software delivery platform
  Drive technical alignment and influence engineering strategy across teams building interdependent, distributed services.
• Mentor engineers and promote best practices, standards, and design patterns for both traditional service development and agent/AI-assisted workflows.
• Lead code and design reviews; drive continuous improvement in software quality, observability, and reliability.
• Partner with cross-functional stakeholders to deliver business value and remove technical roadblocks, including for cloud infrastructure provisioning and multi-tenant isolation.
• Communicate regularly with Product Management to maintain a solid understanding of the product roadmap.
• Ensure effective integration of software across products, platforms, and environments, including emerging agent-to-service integration standards.
• Lead the resolution process for complex, cross-system technical issues; guide root-cause fixes and modifications to prevent recurrence.

• 8+ years of hands-on experience in full lifecycle software development.
• Strong knowledge of software engineering best practices, design patterns, and development methodologies.
• Strong experience with .NET/C# and modern JavaScript/TypeScript front-end frameworks (e.g., React).
• Experience with relational database design, optimization, and performance tuning.
• Experience designing and developing microservices/distributed architectures, including service-to-service authentication and multi-tenant systems.
• Experience with containerized and orchestrated deployments (Docker, Kubernetes/AKS, infrastructure-as-code) and CI/CD pipelines.
• Experience creating and maintaining automated tests (unit, integration, e2e).
  Knowledge of Agile development practices.
• Proven ability to drive technical excellence, influence change, and support cross-team initiatives.
• Ability to communicate technical concepts effectively to both technical and non-technical stakeholders.
• Excellent collaboration, leadership, and problem-solving skills.
• Familiarity using AI tools for development is a real plus — hands-on experience with AI coding assistants (e.g., GitHub Copilot, Claude, Cursor), and ideally exposure to agent/LLM frameworks, agent interoperability standards, or building/operating autonomous coding agents.

• A flexible work philosophy
• Generous paid time off 
• Company paid private health insurance
• Company paid life and disability insurance
• Paid leave for illness, birth parents, non-birth parents, elder caregivers, marriage, adoption of a child and bereavement
• Inclusive and accessible Employee Assistance Program (EAP) to help with everyday challenges
• Christmas and Easter bonuses
• Work-from-home allowance
• Opportunity for strengthening expertise and skills through Paychex’s learning platform, including lessons in English

At Paychex, we know that great talent comes in many forms. If you're passionate about the role but don't check every box, we still encourage you to apply. You might be the right fit - either for this position or another opportunity with us.


Paychex is an equal opportunity employer. We are committed to fostering a respectful and inclusive workplace where all individuals are treated fairly and evaluated based on their qualifications, experience, and merit. We comply with all applicable federal, state, and local laws prohibiting discrimination in employment.