Senior Software Engineer (Full Stack)

As a Senior Software Engineer you will play a critical role in both the sustainment of the current environment and the delivery of new capabilities. The selected individual will develop solutions to complex technical issues and problems that impact multiple areas or disciplines; regularly employ ingenuity and creativity to develop new technical solutions and systems to achieve functional objectives.

You will be immersed in one of our key programmes. On behalf of our central government customer, you will have direct impact on the current and future iterations of one of our most important pieces of critical national infrastructure.

This is a senior individual contributor role. The individual will be a highly experienced engineer who leads by example through day-to-day development, contributes to technical decision-making within their scope, and supports the wider team through mentoring and technical guidance. Overall technical approach is agreed collaboratively with the Technical Lead and Software Architect.

What will I be doing?

• Deliver high-quality, production-ready software through hands-on development, spanning both backend and front-end technologies.
• Develop, debug, test, document, and deploy software enhancements aligned with the Software Development Strategy.

• Contribute to full-stack delivery, including:

• Backend services and REST APIs implemented in Java
• Modern single-page applications implemented using React/TypeScript or equivalent frameworks

Make technical decisions within assigned scope, aligning with agreed architectural direction and escalating broader decisions where appropriate.

Apply strong software engineering practices to ensure solutions are clean, maintainable, well-documented, and fit for long-term operation.

Ensure adherence to established code review standards and quality gates for all changes delivered within the project.

Continuously validate and maintain the build and deployment pipeline for their own changes:

• Make updates as necessary to ensure changes do not break the pipeline
• Act as a guide for other developers to ensure pipeline practices are understood and maintained

Write and maintain unit tests and integration tests as a standard part of development.

Support and contribute to test automation efforts, working closely with the test team (who retain ownership of overall automation outcomes).

Collaborate closely with other engineers, architects, and testers to ensure new and modified software is fully verified prior to promotion.

Support Agile delivery practices, including planning, estimation, backlog refinement, and iterative delivery.

Use and support development tooling and processes, including CI/CD pipelines and integrated security scanning.

Mentor and support less experienced engineers through technical guidance, code reviews, and informal coaching.

Communicate effectively with peers and stakeholders on technical matters, providing clear and well-reasoned input.

What does Leidos need from me?

• Software engineering experience, including substantial hands-on delivery using:

• Java (Java 8 and modern Java versions such as 17 and 21)
• REST API design and implementation

Modern SPA development experience (required) using React and TypeScript, Angular, or Vue.

Strong understanding of design patterns and a solid, structured approach to software development.

Proven experience delivering complex changes in production environments.

Demonstrated experience writing unit and integration tests as a normal part of delivery.

Familiarity with Agile software development processes and working within iterative delivery models.

Familiarity with the Atlassian tool suite (e.g. Jira, Bitbucket, Bamboo), or equivalent tooling, with a solid understanding of CI/CD concepts, workflows, and practices.

Experience working with code review standards, quality gates, CI/CD pipelines, and security scanning processes.

Desirable Skills And Experience

• Familiarity with integration and architectural patterns (e.g. adapters, orchestration patterns such as saga).
• C/C++ experience.
• Perl, Python, and/or bash scripting experience.
• Experience contributing to or supporting test automation initiatives (UI and/or API).

Clearance Requirements: Successful candidates will be required to be willing and able to obtain UK Security Clearances - this requires a minimum of 5 years residency in the UK