Senior Software Engineer
Confirmed on the employer's own hiring board on Oct 19, 2026. First seen by Alion on May 21, 2026. Assystem scores B on the Alion truth index.
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.
The Job Mission
We are looking for a Senior Software Engineer to join the Digital 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.
What you will do
- 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
Essential Skills
- 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
Desired Skills
- Experience with container tooling
- Familiarity with Microsoft tooling, including Power Platform
- Experience with Office document automation, including Excel, Word and PDF generation
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.
You do not need deep expertise in all of these, but you should be comfortable learning and contributing across a varied environment. Our current stack includes, but is not limited to:
C#/.NET, SPython FastAPI/Django, TypeScript, Angular, Vue.js, PostgreSQL, MongoDB, Redis/Valkey, RabbitMQ, Kafka, Azure, S3-compatible storage, Talend, NiFi, Docker, Podman, Kubernetes, Power Platform, and Office document automation tools such as Aspose.
Join Assystem and play a key role in delivering enterprise-wide digital transformation across a global engineering organisation. Work alongside highly experienced software and data professionals to build innovative solutions supporting critical infrastructure projects while developing your career in a collaborative and forward-thinking environment.
Benefits include:
Hybrid Working Opportunity
Flexible working hours
Pension scheme (8% company contribution / 4% personal contribution)
25 days’ paid annual leave + bank holidays + option to buy or sell days
Professional fees reimbursed
Employee referral scheme
Competitive Sick Pay - Support when you need it
Income Protection & 3x Salary Death-in-Service Cover
Free Digital Gym Access - Expert-led fitness classes
24/7 Employee Support Line - Mental health, financial & legal help
We are committed to equal treatment of candidates and promote, as well as foster all forms of diversity within our company. We believe that bringing together people with different backgrounds and perspectives is essential for creating innovative and impactful solutions. Skills, talent, and our people’s ability to dare are the only things that matter.
Bring your unique contributions and help us shape the future!
NOTICE TO CANDIDATES ON RECRUITMENT FRAUD - We are committed to safeguarding candidates from fraudulent activity associated with our recruitment process. Please note that we will never offer specialist CV writing services, request payment or ask for sensitive personal information during the recruitment process.
NOTICE TO CANDIDATES ON RECRUITMENT FRAUD - We are committed to safeguarding candidates from fraudulent activity associated with our recruitment process. Please note that we will never offer specialist CV writing services, request payment or ask for sensitive personal information during the recruitment process.
We are committed to equal treatment of candidates and promote, as well as foster all forms of diversity within our company. We believe that bringing together people with different backgrounds and perspectives is essential for creating innovative and impactful solutions. Skills, talent, and our people’s ability to dare are the only things that matter !. Bring your unique contributions and help us shape the future.