Senior Full Stack Developer

Leidos•Reston, VA

About The Position

Leidos is seeking a Senior Full Stack Developer / Senior Software Engineer to guide technical support, development, and expansion of its core application ecosystem. The role takes hands-on ownership of a modern stack built on React.js, Node.js, Python, and PostgreSQL. Initial work includes directly transitioning existing internal tools and core applications into the supported ecosystem without complex migration planning. The developer will scale active applications, design new features, and collaborate with technical experts to build new software applications for emerging requirements. The role also supports integration of AI-driven tools, chat interfaces, workflows, and data pipelines into the core ecosystem, working in a collaborative, fast-moving small team. The senior developer serves as a technical lead for active web applications, overseeing system health, code quality, technical design, maintenance, troubleshooting, and operational reliability. They architect and build features and applications, optimize Python backend processing, scale Node.js services, and design high-performance APIs using FastAPI or RESTful approaches. They support emerging features such as chat interfaces, RAG concepts, and intelligent application components; conduct code reviews; establish testing strategies; mentor a Mid-Level developer; and create and maintain foundational repositories, boilerplates, and coding standards for the React/Node/Python stack. The position requires an active TS/SCI with Polygraph and either a bachelor’s degree with 12–15 years of relevant experience or a master’s degree with 10–13 years of relevant experience. A doctorate in a technical domain may also be held. The successful candidate develops innovative solutions through research and integration of best practices, recommends and develops technical solutions, products, or standards supporting program strategy and operations, and performs programming, documentation, configuration management, testing, and bug fixing throughout the software release lifecycle.

Requirements

Must have an active TS/SCI with Polygraph.
Bachelor’s degree and 12–15 years of prior relevant experience, or a master’s degree and 10–13 years of prior relevant experience.
Strong experience building production-grade web applications using React.js and Node.js.
Strong Python experience for backend services, background jobs, or data-processing pipelines.
Deep knowledge of building robust RESTful APIs, specifically with frameworks such as FastAPI.
Strong command of PostgreSQL or similar relational databases, including schema design, indexing, complex joins, and query optimization.
Comfortable reading and understanding legacy C#/.NET structures to guide simple application transitions; writing or maintaining C# is not required.
Deep familiarity with Git and CI/CD concepts.
Ability to develop innovative solutions through research and integration of best practices.
Ability to recommend and develop technical solutions, products, and standards in support of program strategy and operations.

Nice To Haves

Practical experience working in an Agile development environment such as Scrum, Kanban, or similar sprint-based workflows.
Experience or familiarity supporting AI-adjacent application features, such as conversational or chat interfaces, vector databases, or Retrieval-Augmented Generation (RAG) architectures.
Experience with Docker configurations, container security, or image hardening.
Thrives in a small team environment with high autonomy, direct business impact, and less corporate red tape.
Eager to collaborate with technical experts to ideate and build new platforms and solve new problems from the ground up.
Pragmatic focus on delivering clean, working software on time rather than over-engineering frameworks.

Responsibilities

Act as a core technical lead for active web applications, responsible for system health, code quality, and technical design.
Oversee day-to-day application maintenance, troubleshooting, and operational support to ensure reliability.
Manage direct transitions of core tools into the supported ecosystem with minimal friction.
Architect and build high-impact features and new applications.
Optimize Python backend processing scripts and scale Node.js services.
Design high-performance APIs, including FastAPI and RESTful APIs.
Assist with development and technical integration of chat interfaces, RAG concepts, and intelligent application components.
Conduct code reviews and establish testing strategies.
Mentor a Mid-Level developer.
Set up and maintain foundational repositories, boilerplates, and clean code standards for the React/Node/Python stack.
Perform programming, documentation, configuration management, testing, and bug fixing involved in creating and maintaining applications and frameworks through the software release lifecycle.