Senior Developer

Senior Developer

Are you ready for your next career challenge? Role overview:
Provide hands‑on technical leadership for the design, development, integration and support of ESCS software capabilities. The Senior Developer establishes engineering patterns, leads complex implementation work and mentors developers while maintaining a strong focus on security, quality and operability.

Lead software design and delivery within a capability team. Translate architecture and requirements into maintainable engineering solutions. Raise engineering quality through standards, reviews, automation and mentoring.

• Design, build, test and maintain cloud‑based applications, services and integrations.
• Define and apply patterns for APIs, microservices, event‑driven integration and data exchange.
• Lead code reviews, technical design reviews and complex defect resolution.
• Embed secure coding, automated testing, observability and operational readiness.
• Contribute to CI/CD pipelines, infrastructure automation and release practices.
• Create clear technical design and support documentation.
• Estimate work, identify technical risk and collaborate with architecture, analysis, data, test and infrastructure colleagues.
• Mentor developers and support consistent engineering practices across teams.

• Strong capability in relevant languages and frameworks such as C#/.NET, Java and/or Python RESTful API and integration development
• Microservices and event‑driven architecture
• Cloud‑native engineering on Azure and/or AWS
• Secure coding and software assurance
• Automated unit, integration and component testing
• CI/CD, Git workflows and Dev Sec Ops  practices
• Observability, logging, monitoring and diagnostics
• Infrastructure as Code awareness, including Terraform or equivalent
• Technical design documentation and mentoring

• Delivery of production software in complex enterprise environments.
• Hands‑on experience of cloud services, APIs, automated build and deployment pipelines.
• Experience leading technical implementation, code quality and engineering decisions.
• Experience integrating with third‑party or SaaS platforms.

• High‑volume transactional or supply chain systems.
• SaaS customisation, extension and integration.
• Containers and orchestration platforms.
• AI‑assisted development used within approved engineering and security controls.

• Software is secure, testable, observable and maintainable.
• Design decisions and interfaces are clearly documented.
• Engineering risks are surfaced early and resolved collaboratively.
• Developers receive practical technical guidance and constructive review.

SC required to start, SC required for the role Leidos UK

Join our team and discover a culture of collaboration, innovation, diversity, trust, caring management, communication transparency, work‑life balance, and overall job satisfaction.

At Leidos we are PASSIONATE about customer success, UNITED as a team and INSPIRED to make a difference. We offer meaningful and engaging careers, a collaborative culture, and support for your career goals, all while nurturing a healthy work‑life balance.

• Contributory Pension Scheme
• Private Medical Insurance
• 33 days Annual Leave (including public and privilege holidays)
• Access to Flexible benefits (including life assurance, health schemes, gym memberships, annual buy and sell holidays and a cycle to work scheme)
• Flexible Working Scheme

We welcome applications from every part of the community and are committed to a truly diverse and inclusive culture. We foster a sense of belonging, welcoming all perspectives and contributions, and providing equal access to opportunities and resources for everyone. If you have a disability or need any reasonable adjustments during the application and selection stages please let us know, and we will respond in a way that best fits your needs.

Leidos UK & EUROPE - we work to make the world safer, healthier, and more efficient through technology, engineering and science. Leidos is a growing company…