Senior Software Engineer

Excellence Centre (DEC) UK. You will help design, build and support secure, maintainable software products and reusable components that improve performance, decision‑making and delivery across the business and for our clients. This is a hands‑on role in a small, senior team, with real scope to influence technical direction, engineering standards and solution design. You will work across a varied technology environment, contribute from discovery through to production support, and collaborate closely with colleagues in the UK, India and, where relevant, France.

We are not looking for someone who knows every tool in our stack. We are looking for strong engineering fundamentals, sound judgement, adaptability and a practical approach to solving problems.

• Work closely with senior stakeholders to understand requirements
• Design, build, test, deploy and support software applications, services and reusable components
• Produce pragmatic technical designs that balance quality, security and maintainability
• Work across back end services, integrations and user‑facing applications
• Contribute to engineering standards through code review, testing, CI/CD and documentation
• Design secure APIs and integrations across digital products, enterprise systems and data services
• Work closely with data engineers on APIs, events and data contracts
• Support and mentor others through pairing, review and day‑to‑day collaboration
• Help make sensible technology choices that keep solutions supportable over time

• 8 years experience
• Practical use of, or strong interest in use of AI‑assisted development tools in a responsible delivery environment
• Experience delivering production software end to end, working closely with stakeholders
• Front end, back end development experience
• Experience designing APIs and integrating with enterprise systems and data services
• Good understanding of software design principles and modern engineering practice
• Experience with automated testing and CI/CD
• Experience working with relational databases
• Familiarity with database and caching technologies
• Understanding of secure coding and modern authentication and authorisation
• Experience delivering software in cloud‑hosted environments, e.g. Azure
• Ability to work effectively across a mixed technology estate
• Strong communication skills and experience working in collaborative teams
• Experience mentoring others through review, pairing and practical support
• Security and eligibility:
  Depending on project requirements, you may need to meet UK residency criteria and achieve UK security clearance, such as BPSS and potentially SC.

• Experience with container tooling
• Familiarity with Microsoft tooling, including Power Platform
• Experience with Office document automation, including Excel, Word and PDF generation

About Assystem Today, Assystem is among the top three independent nuclear engineering firms worldwide. With over 60 years of experience in highly regulated sectors, the group supports public and industrial stakeholders in the execution of complex and strategic infrastructure projects, subject to high safety and security requirements. Assystem mobilizes 8,000 experts in 13 countries and intervenes across the entire project lifecycle, in engineering, project management and digital solutions.

In line with our 2030 Business Plan, we are delivering a major enterprise transformation initiative – the Assystem Transformation Programme (ATP) – to streamline and harmonise business operations across all geographies. This includes optimising our processes, redesigning and redeveloping our Integrated Management System, and moving from document‑centric to data‑centric ways of working.

We are looking for a Senior Software Engineer…