Principal Software Engineer Jobs in Plano, TX

8116 - Midtown Office - 2220 W. Broad Street, Richmond, Virginia, 23220

CarMax, the way your career should be!

About the Team

The Developer Experience team is the internal platform and enablement engine for CarMax Technology. Our mission is to make every engineer at CarMax faster, more confident, and better equipped through the tools, platforms, and practices they use every day. We own the developer portal, golden path frameworks, and the agentic AI tooling platform: MCP integrations, skills, agents, and the configuration infrastructure that makes AI-assisted development work at scale and is reshaping how software gets built here. We sit at the intersection of platform engineering and developer advocacy, and we treat the developer as our customer.

What You Will Do – Essential Responsibilities

• Design, build, and evolve the developer platform, including the developer portal, golden path templates, and onboarding frameworks. These serve as the foundation for how CarMax engineers build, run, and ship software.

• Build and maintain the integration layer that makes agentic AI development work at scale for 500+ engineers: MCP servers, skills, agent workflows, multi-model routing configuration, and the tooling instrumentation that lets the organization understand how engineers are working.

• Design and govern the MCP and skills ecosystem: defining patterns for how integrations are built, approved, documented, and maintained so that teams across CarMax can build on a stable, consistent platform rather than navigating a one-off approval process for every new capability.

• Establish and champion engineering best practices: coding standards, reusable libraries, API patterns, and infrastructure as code across the Developer Experience portfolio.

• Share what you know. When you build something that works, help others understand why through documentation, pairing, or a spot on the learning series agenda. Engineering Experience is a community effort and this role contributes to it.

• Stay current in a field that does not slow down. The model landscape, the MCP specification, and agentic workflow patterns are all changing fast, and part of this role is knowing what’s worth adopting, what’s worth watching, and what’s noise. Bring that signal back to the team and the broader engineering community.

• Market your innovative ideas internally and evolve them through feedback, driving adoption across engineering communities of practice.

Purpose of the Role

Principal Engineers within the Developer Experience team sit at the heart of how CarMax builds software. They are hands-on technical leaders who don’t just write excellent code, they shape the platforms and practices that multiply the effectiveness of every engineer in the organization. Recognized as technical authorities and platform advocates, they are responsible for building and evolving the systems that underpin developer productivity: the agentic AI tooling platform, MCP and skills ecosystem, developer portal, and the integrations that connect CarMax’s engineering environment to the AI tools engineers use every day.

It takes a genuine passion for developer experience to build the tools that make other engineers faster. Working collaboratively as part of the Engineering Experience group, you will engage in the full development lifecycle: understanding the real challenges developers face, designing platform solutions at scale, integrating emerging AI capabilities into the SDLC, and delivering outcomes that are measurable and durable. You balance developer needs with platform reliability and know how to ship technical solutions that compound in value over time. Creative, curious, and technically deep, you thrive at the intersection of platform engineering and AI innovation. You are energized by a landscape that keeps moving: new models, evolving specifications, and platform questions that do not yet have established answers. You never stop learning, and you bring others along as you go.

Qualifications and Requirements

Basic Qualifications

• Bachelor’s degree in Computer Science, Engineering, or a related field, or equivalent alternative education, skills, and/or practical experience is required.

• 8+ years of experience with .NET Core/C#/Microsoft Azure offerings.

• Strong teamwork and leadership skills, ability to learn quickly, excellent written and spoken communication required.

• Demonstrated ability or strong interest in technical leadership and mentoring engineers.

• Experience working within a product or platform organization using Agile and DevOps methodologies.

Experience in the Following Required

AI & Developer Tooling

• Agentic AI coding workflows in daily practice: you have built with these tools, not just read about them

• Skills and agent workflow authoring: configuration-as-code for AI tools, slash commands, reusable workflow patterns

• Multi-model environments: model selection by task type, cost and quality tradeoffs across frontier and open-weight models, routing configuration

Platform & DevOps

• GitHub and Git-based workflows (branching, PRs, code reviews)

• Azure DevOps / Azure Boards

• Tooling telemetry and instrumentation: understanding how distributed systems are actually used across a large population

• Authentication and authorization patterns (PATs, OAuth, SSO) as applied to developer tooling and MCP integrations

• Infrastructure as Code (ARM/Bicep): sufficient depth to deploy and maintain the Azure-hosted components this role will own

Backend & Cloud

• Advanced .NET / C# application development

• Microsoft Azure (PaaS, IaaS, CaaS)

• RESTful API design and implementation

• Distributed systems and microservices architecture

• Node.js / TypeScript: relevant to MCP server development and the broader tooling ecosystem alongside .NET

Experience in the Following Preferred

• MCP development: protocol fundamentals (studio, SSE, Streamable HTTP), tool and resource definitions, local vs. remote deployment patterns, the CarMax wrapper pattern for third-party MCPs, and the context window and token cost discipline that separates a well-built MCP from one that degrades model performance

• Internal developer portals: their role in discoverability, onboarding, and information architecture for engineering teams

• Experience building tools or platforms that other engineers depend on, not just using them

• Experience mentoring and developing other engineers

• Familiarity with RAG architecture, vector search, or knowledge graph approaches, adjacent to active work in the Onramp AI enhancement space

• Experience working within a product organization

• Active engagement with the AI developer tooling community: you follow where this is going, not just where it has been

Work Location and Arrangement: This role will be based out of the Richmond Midtown or Plano Tech hub and have a Hybrid work arrangement.

• Associates based in Richmond work on-site 4 days per week.

• Associates based in Plano work onsite 2 days per week

Work Authorization: Applicants must be currently authorized to work in the United States on a full-time basis. Sponsorship will not be considered for this specific role.

About CarMax

CarMax disrupted the auto industry by delivering the honest, transparent and high-integrity experience customers want and deserve. This innovative thinking around the way cars are bought and sold has helped us become the nation’s largest retailer of used cars, with over 200 locations nationwide.

Our amazing team of more than 25,000 associates work together to deliver iconic customer experiences. Along the way, we help every associate grow their career and achieve their best, at work and in their community. We are recognized for our commitment to training and diversity and are one of the FORTUNE 100 Best Companies to Work For®.

Our Commitment to Diversity and Inclusion:

CarMax is committed to bringing together people from different backgrounds and perspectives, providing employees with a safe, welcoming, and inclusive work environment.

CarMax is an equal opportunity employer, and all qualified candidates will receive consideration for employment without regard to age, race, color, religion, sex, sexual orientation, gender identity, genetic information, national origin, protected veteran status, disability status, or any other characteristic protected by law.

Upon an applicant's request, CarMax will consider reasonable accommodation to complete the CarMax Job Application.