Senior Software Engineer

Staff Software Engineer, Defense Applications Location: Fort Belvoir, Virginia - Onsite
Openings: 2
Clearance Requirement: Must have an active Secret clearance
Employment Type: Direct hire or temp to perm

Position Overview System One IT is seeking two Staff Software Engineers to design and deliver mission-focused applications supporting a Department of Defense customer at Fort Belvoir, Virginia.
This is a senior, hands-on engineering opportunity for professionals who can own substantial software capabilities from initial architecture through production deployment. You will build user-facing applications, backend services, APIs, and data integrations while working directly with Army users and product designers.
The ideal candidate has strong full stack development experience, technical leadership capabilities, and experience building applications on Palantir Foundry or a comparable enterprise data platform. Responsibilities

• Own the architecture, development, and delivery of user-facing defense applications
• Build responsive web interfaces, backend services, APIs, and data integrations
• Develop applications using Palantir Foundry capabilities and modern web frameworks
• Collaborate directly with Army users and product designers to understand operational workflows and refine application capabilities
• Establish and promote effective engineering practices for architecture, testing, code review, security, CI/CD, and production operations
• Diagnose and resolve complex application, data, and integration issues across the technology stack
• Mentor engineers and contribute to technical decisions across the broader platform
• Maintain high standards for software quality, reliability, security, and maintainability

• Bachelor’s degree in computer science, software engineering, or a related discipline, or equivalent practical experience
• Eight or more years of professional software engineering experience
• Strong proficiency with JavaScript or Type Script, React, and modern web application development
• Experience developing backend services, APIs, and data-intensive applications
• Experience building applications on Palantir Foundry or a comparable enterprise data platform
• Demonstrated ownership of a significant software capability from architecture through production deployment
• Experience supporting a Department of Defense customer
• Active Secret clearance

• Experience supporting the U.S. Army
• Hands-on experience with Palantir Foundry, Army Vantage, OSDK, Workshop, or AIP
• Experience developing applications with Python, Java, Go, or Node.js
• Familiarity with Army acquisition or program management processes
• Experience with cloud platforms, Dev Sec Ops  practices, CI/CD, and secure production environments
• Experience using AI-assisted software development tools

System One, and its subsidiaries including Joulé and Mountain Ltd., are leaders in delivering outsourced services and workforce solutions across North America. We help clients get work done more efficiently and economically, without compromising quality. System One not only serves as a valued partner for our clients, but we offer eligible employees health and welfare benefits coverage options including medical, dental, vision, spending accounts, life insurance, voluntary plans, as well as participation in a 401(k) plan.

System One is an Equal Opportunity Employer. All qualified applicants will receive consideration for employment without regard to race, color, religion, sex (including pregnancy, childbirth, or related medical conditions), sexual orientation, gender identity, age, national origin, disability, family care or medical leave status, genetic information, veteran status, marital status, or any other characteristic protected by applicable federal, state, or local law.