Senior Software Engineer

Assystem UK Ltd; Bagstone; Hybrid; GBP 90,000 - 120,000; Full time

Benefits offered by this job

Hybrid Working

Flexible working hours

Pension scheme (8% company / 4% лич)

25 days’ paid annual leave + bank hols

Professional fees reimbursed

Employee referral scheme

Sick pay

Income protection & 3x salary death-in

Death-in-Service Cover

Digital gym access

24/7 employee support line

Job summary

Assystem UK Ltd is seeking a Senior Software Engineer to join the Digital team. You will design, build, and support secure software products and reusable components across a varied tech stack, collaborating with colleagues in the UK, India, and France.

The role offers hands-on work in a senior team with influence on technical direction and engineering standards. You will contribute from discovery through production support, delivering APIs and integrations while mentoring others and advancing

Qualifications

• 8 years of professional software development experience.
• Experience delivering production software end to end and collaborating with stakeholders.
• Frontend and backend development experience.
• Experience designing APIs and integrating with enterprise systems.
• Strong understanding of software design principles and modern engineering practices.
• Experience with automated testing and CI/CD.
• Experience with relational databases and caching technologies.
• Understanding of secure coding and modern authentication and authorization.
• Experience delivering software in Azure or similar cloud environments.
• Ability to work effectively across a mixed technology estate.
• Strong communication and collaboration skills; mentoring others.
• Security clearance: UK residency criteria and possible BPSS/SC.

Responsibilities

• 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.

Skills

8 years experience

AI-assisted development

End-to-end delivery

Full stack

API design

Software design principles

Automated testing & CI/CD

Relational databases

Caching technologies

Secure coding & auth

Cloud environments (Azure)

Cross-functional collaboration

Security clearance eligibility (UK)

Tools

Container tooling

Power Platform

Office document automation (Excel/Word/PDF)

Job description

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

Qualifications

• 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.

Desired Skills

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

Company Description

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.

Job Mission

We are looking for a Senior Software Engineer to join the Digital C#/.NET, S+Python 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

• 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 your unique contributions and help us shape the future!

Summary Type: Full‑time Function: Information Technology Experience level: Mid‑Senior Level Industry: Information Technology And Services