KGS is currently seeking an accomplished Senior Full Stack Software Engineer/Developer to spearhead the engineering, enhancement, and architectural modernization of core Line of Business (LOB) applications operating within a secure Department of War (DoW) enterprise environment. The ideal candidate will bring strong hands-on experience in full-stack development with React, JavaScript, and Node.js, and thrive in an Agile team setting. This role requires an understanding of modern software development practices, strong problem-solving abilities, and the ability to collaborate across teams to deliver secure, high-quality solutions.
A defining operational imperative of this engagement is that we are actively maintaining mission-critical legacy applications while driving strategic modernization. The selected senior engineer will operate across a sophisticated dual-track paradigm: ensuring uninterrupted operational readiness and fidelity of mature enterprise systems, while concurrently architecting, refactoring, and migrating these capabilities toward resilient, modular, and cloud-ready architectures.
Operating under the technical direction of the Software Development Lead and Solutions Architect, the Senior Software Developer will play an integral role throughout the full software development lifecycle within a disciplined Agile/Scrum framework. The incumbent must demonstrate authoritative, hands-on development expertise across the foundational stack: React, modern enterprise Java Spring Boot, and robust relational database engineering utilizing Microsoft SQL Server and/or MySQL.
Furthermore, demonstrable exposure to complementary enterprise frameworks—including modern .NET (.NET 8+ / C#) and Node.js—alongside practical experience within hyperscale cloud ecosystems (AWS, GCP, or Azure) represents a high-value differentiator. Centralizing all source code collaboration and automated CI/CD pipelines within GitLab, this role demands exceptional analytical acumen, disciplined engineering rigor, and an uncompromising commitment to DoW cybersecurity standards.
Essential Functions, Responsibilities & Duties may include, but are not limited to:
Full-Stack Architecture, Engineering & Legacy Modernization
Dual-Track Operational Execution: Uphold baseline stability, performance, and defect resolution for active legacy enterprise applications, while systematically engineering migration roadmaps that decompose monolithic architecture into decoupled, maintainable, and cloud-aligned services.
Full-Lifecycle Application Development: Leverage rigorous software engineering principles to design, construct, optimize, and sustain high-throughput, secure web applications utilizing React for user interfaces, Java Spring Boot for robust business logic, and Microsoft SQL Server / MySQL for resilient data persistence.
Modernization Strategy & Refactoring: Formulate and implement clean code refactoring, domain-driven decomposition, and containerization patterns, transitioning legacy routines to scalable microservices and modern design paradigms without disrupting continuous mission operations.
Process Automation & AI-Enabled Velocity: Proactively evaluate and integrate emerging AI-assisted developer capabilities, automated code-generation tools, and streamlined workflows to enhance developer velocity, technical accuracy, and lifecycle efficiency.
Front-End Engineering & User Experience
Modern Interface Development: Demonstrate mastery of React, ES6+ JavaScript, HTML5, and CSS3 to deliver intuitive, highly responsive, and component-driven user interfaces.
Accessibility & Interface Modernization: Modernize disparate, legacy front-end presentations into unified, reusable design systems that strictly conform to federal Section 508 accessibility mandates and DoW user experience benchmarks.
Backend Services, Middleware & Distributed Systems
Enterprise Service Implementation: Architect, implement, and maintain highly scalable backend microservices and enterprise…