Leidos is seeking a Principal Software Engineer (C#) to work for the Security Enterprise Solutions (SES) business unit in Vista, CA. The SES business unit at Leidos designs and manufactures highly complex security equipment for use at border crossings, airports, seaports, and other transportation mechanisms. Our products include radiation detectors and spectrometers, X-ray and gamma ray scanners for cars, trucks and trains, and CT explosives detection equipment for airline passenger baggage. The ultimate goal for this position will be to update existing design as well as introduce new products to our already extensive line of security detection products. The products being developed through this effort are truly novel, and will make travel and trade safer, healthier, and more efficient on a global level.*We are seeking candidates local to Vista CA that have the ability to work a hybrid schedule (3 days remote, 2 days onsite) The Principal Software Engineer (C#) will serve as a senior member of the technical team, providing technical leadership and expertise while fostering collaboration and team consensus. This individual will play a key role in driving innovation, enhancing security compliance, and mentoring other engineers. As part of a cross-functional team, the Principal Software Engineer will develop and maintain cargo inspection detection systems for the Ports and Borders group at Leidos. This role requires advanced technical expertise, a commitment to best practices, and a focus on delivering high-quality, secure software solutions.Key Responsibilities:Technical Contribution and Collaboration:<ul><li>Contribute to the design, development, testing, and maintenance of services, simulators, and diagnostics (WPF and Blazor) using C#.</li><li>Provide technical leadership by guiding architectural decisions, fostering team collaboration, and ensuring alignment with best practices.</li><li>Lead the adoption of tools, including AI-based software development tools, to enhance productivity and innovation.</li><li>Promote team buy-in and shared ownership of technical solutions and processes.</li></ul>Software Development and Security Compliance:<ul><li>Develop software that adheres to industry security standards and enhances the security compliance of the codebase and coding practices.</li><li>Utilize object-oriented design principles, practices, and patterns to ensure the codebase is reusable and maintainable.</li><li>Apply Test-Driven Development (TDD) and Continuous Integration to ensure high-quality, continuously tested code.</li><li>Collaborate with Electrical Engineering, Mechanical Engineering, and Scientists to meet customer requirements.</li></ul>Problem Solving and Innovation:<ul><li>Evaluate customer problems, troubleshoot issues, and assist Field Service Engineers with problem resolution.</li><li>Drive innovation by researching and integrating best practices to develop cutting-edge solutions.</li></ul>Business Development Support:<ul><li>Assist with business development efforts, including initial concept solutioning/architecting, conops, estimating, and technical bid and proposal work.</li><li>Evaluate and explain tradeoffs between cost, quality, and speed of delivery to less technical members of the business development team.</li></ul>Customer Interaction:<ul><li>Interact with customers of varying technical levels to explain and defend approaches, limitations, and solutions.</li><li>Answer technical questions and work collaboratively with customers to develop solutions that meet their needs.</li></ul>Project Estimation and Sustainability:<ul><li>Develop project estimates for budgeting and scheduling, including allocations for sustaining engineering, obsolescence management, and technical debt remediation.</li><li>Evaluate and recommend technical directions for sustaining and obsolescence activities to ensure long-term product viability.</li><li>Incorporate forward-thinking strategies into estimates to support sustainable product lines and reduce long-term risks.</li></ul>Communication and Reporting:<ul><li>Communicate proactively and effectively within a small cross-functional development team environment.</li><li>Report project status and issues to management as required</li></ul>Required Skills:<ul><li>BS Degree and 12+ years of experience or Masters Degree with 10+ years of experience. May consider additional years of experience in lieu of a degree.</li><li>Must have the ability to obtain a Public Trust clearance.</li><li>Strong programming background with production product development experience in C# required.</li><li>Mastery of object-oriented design (OOD) principles and practices.</li><li>Proven experience in software architecture and leadership roles.</li><li>Expertise in Agile methodologies, including TDD and Continuous Integration.</li><li>Ability to create design documentation, requirements specifications, and other technical documentation.</li><li>Strong troubleshooting and bug-fixing skills.</li><li>Effective communication and collaboration skills in cross-functional team environments.</li><li>Ability to explain technical tradeoffs and solutions to non-technical stakeholders.</li><li>Experience developing project estimates for budgeting and scheduling, including allocations for sustaining engineering and technical debt remediation.</li><li>Must be willing to travel abroad. If travel is necessary, typically it will be &lt; 10%.</li></ul>Desired Skills:<ul><li>Proficiency with AI-based software development tools.</li><li>Experience developing software that complies with industry security standards.</li><li>Experience identifying code smells and utilizing refactoring techniques to reduce entropy in the codebase.</li><li>Proficiency with UML and documented design methodologies.</li><li>Experience with revision control (e.g., Git), multi-threading, TCP/IP networking, bus architectures, Web Services, Blazor, containers (e.g., Docker), Visual Studio, C++, SQL Server, and interfacing with real-time/embedded systems.</li><li>Knowledge of image processing techniques.</li></ul><ul></ul>Check out the links below to learn more about Security Enterprise Solutions (SES) <a href="https://careers.leidos.com/pages/security-enterprise-solutions" target="_blank">https://careers.leidos.com/pages/security-enterprise-solutions</a>      <a href="https://www.leidos.com/markets/aviation/security-detection" target="_blank">https://www.leidos.com/markets/aviation/security-detection</a>  At Leidos, we don’t want someone who fits the mold—we want someone who melts it down and builds something better. This is a role for the restless, the over-caffeinated, the ones who ask, “what’s next?” before the dust settles on “what’s now.”If you’re already scheming step 20 while everyone else is still debating step 2… good. You’ll fit right in.<h2></h2><h2></h2><h2>Original Posting:</h2>September 11, 2025<div><div><div><div><div><div><div>For U.S. Positions: While subject to change based on business needs, Leidos reasonably anticipates that this job requisition will remain open for at least 3 days with an anticipated close date of no earlier than 3 days after the original posting date as listed above.</div></div></div></div></div></div></div><div></div><h2>Pay Range:</h2>Pay Range $126,100.00 - $227,950.00The Leidos pay range for this job level is a general guideline only and not a guarantee of compensation or salary. Additional factors considered in extending an offer include (but are not limited to) responsibilities of the job, education, experience, knowledge, skills, and abilities, as well as internal equity, alignment with market data, applicable bargaining agreement (if any), or other law.

Leidos Holdings

Principal Software Engineer C#

Leidos Holdings

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