Senior Full Stack Developer

Leidos is looking for a Senior Full Stack Developer / Senior Software Engineer to guide the technical support, development, and expansion of our core application ecosystem. In this role, you will take immediate hands on ownership of our modern stack built on React.js, Node.js, Python, and PostgreSQL.

Your initial focus will include overseeing a straightforward, simple transition of existing web applications (internal tools and core applications) into our ecosystem. This is a direct, functional transition without the need for complex, heavy migration planning.

As a senior member of the team, you will help scale active applications, design new features, and collaborate with other innovative technology experts to build brand-new software applications from scratch to fill emerging requirements. You will lend your robust engineering skills to support our modern features, including assisting with the integration of AI-driven tools, chat interfaces, workflows, and data pipelines into our core ecosystem. You will work closely within a highly collaborative, fast-moving small team environment.

Technical Execution & Application Support

• Technical Ownership: Act as a core technical lead for all active web applications, taking responsibility for their overall system health, code quality, and technical design.
• Application Support: Oversee day-to-day maintenance, troubleshooting, and operational support to ensure application reliability.
• Seamless Transitions: Manage the simple, direct transition of core tools into our supported ecosystem with minimal friction.

Greenfield Development & Innovation

• New Feature & App Creation: Architect and build high-impact features, optimize backend processing scripts in Python, scale Node.js services, and design high-performance APIs (FastAPI/RESTful).
• Modern Integration Support: Assist with the development and technical plumbing required for emerging features, including chat interfaces, RAG concepts, and intelligent application components.
• Code Quality & Mentorship: Conduct code reviews, establish testing strategies, and mentor a Mid-Level developer to maintain a pristine codebase.
• Foundational Codebases: Set up and maintain foundational repositories, boilerplates, and clean code standards for the React/Node/Python stack.

Basic Qualifications

• Must have an active TS/SCI with Polygraph

• BS degree and 12 - 15 years of prior relevant experience or Masters with 10 - 13 years of prior relevant experience. May possess a Doctorate in technical domain.
• Develops solutions that are highly innovative, and achieved through research and integration of best practices.
• Recommends and develops new technical solutions, products, and/or standards in support of the program’s strategy and operations.

• Duties include computer programming, documenting, managing configuration, testing, and bug fixing involved in creating and maintaining applications and frameworks involved in a software release life cycle and resulting in a software product.

• Expertise in JavaScript/TypeScript Ecosystems: Strong experience building production-grade web applications using React.js and Node.js.
• Python & API Proficiency: Strong experience using Python for backend services, background jobs, or data processing pipelines, with deep knowledge of building robust RESTful APIs (specifically using frameworks like FastAPI).
• Database Design: Strong command of PostgreSQL (or similar relational databases), including schema design, indexing, complex joins, and query optimization.
• C# / .NET Literacy (Read-Only): You do not need to write or maintain C# moving forward, but you must be comfortable reading and understanding legacy structures to help guide simple application transitions.
• Modern Tooling: Deep familiarity with Git and CI/CD concepts.

Preferred Qualifications

• Agile Frameworks: Practical experience working effectively within an Agile-based development environment (Scrum, Kanban, or similar sprint-based workflows).
• AI & Modern Workflow Familiarity: Practical experience or familiarity supporting AI-adjacent application features, such as conversational/chat interfaces, vector databases, or Retrieval-Augmented Generation (RAG) architectures.
• Containerization (Docker): Experience with Docker configurations, container security, or image hardening is a plus, but containerization is not a strict requirement for this role.

Preferred Soft Skills & Experience

• The "Small Team" Mindset: Thrives in a small team environment where you have high autonomy, direct business impact, and less corporate red tape.
• Innovation & Ideation: Eager to brainstorm with other technical experts to build new platforms and solve fresh problems from the ground up.
• Pragmatic Delivery: Focused on shipping clean, working software on time rather than over-engineering complex frameworks.

If you're looking for comfort, keep scrolling. At Leidos, we outthink, outbuild, and outpace the status quo - because the mission demands it. We're not hiring followers. We're recruiting the ones who disrupt, provoke, and refuse to fail. Step 10 is ancient history. We're already at step 30 - and moving faster than anyone else dares.

Original Posting:

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.

Pay Range:

The 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.