Senior Software Engineer
Job description
Original text imported from Reed
FDM is a global business and technology consultancy seeking a Senior Software Engineer to work for our client within the defence and national security technology sector. This is initially a 12-month contract with very good prospects to extend and will be a hybrid role based in London with a requirement to attend the office at least one day per week and with up to two days’ notice when required.
Our client is a UK based technology company delivering secure unified communications and information sharing platforms for national security and defence users. The role will support development across their existing secure communications platform as well as a new AI enabled decision support product. This is a senior position suited to an engineer who can work with a high degree of autonomy, contribute to technical direction and support less experienced engineers within a small, highly capable team operating in a secure environment.
Responsibilities:
- Designing, developing and maintaining features across secure communications and decision support platforms
- Building and maintaining backend services using C# and related technologies
- Developing and enhancing user interfaces using React
- Contributing to security focused system design when working with highly sensitive data
- Taking ownership of work items, collaborating closely with engineers, product specialists and stakeholders and, at senior level, contributing to mentoring and technical discussions
- Strong commercial experience in backend development using C# and the .NET ecosystem
- Frontend development experience using React or a similar modern JavaScript framework
- Solid understanding of software engineering fundamentals and agile delivery practices
- Experience working in live production environments, ideally within regulated, government or secure systems
- Eligibility for BPSS clearance and preferably SC clearance or willingness to undergo SC clearance
- Minimum of 5 years’ experience in a software engineering role
FDM is an award-winning global leader in tech and business talent solutions, backed by more than 35 years of industry experience. We have centres across Europe, North America, and Asia-Pacific, and a global workforce of over 2500 employees. FDM has shown exponential growth throughout the years, firmly establishing itself as an award-winning employer, currently listed on the FTSE4Good Index and as a 2026 Financial Times UK ‘Best Employer’.
Diversity and Inclusion
FDM Group is an equal opportunity employer, and all qualified applicants will receive consideration for employment without regard to race, colour, religion, sex, sexual orientation, national origin, age, disability, veteran status or any other status protected by federal, provincial or local laws.
Why join us
- Career coaching, mentoring and access to upskilling throughout your entire FDM career
- Assignments with global companies and opportunities to work abroad
- Opportunity to re-skill and up-skill into new areas, develop non-linear career paths and build a skillset within your field
- Annual leave and work-place pension
Key skills
AI-extracted from the job advert
Application advice
5 AI-generated recommendations to maximise your chances.
⭐ Highlight your C# .NET backend experience prominently as this is the core technology stack mentioned
🔒 Emphasise any security clearance eligibility or experience with regulated/government systems
🎯 Showcase React frontend skills alongside backend expertise to demonstrate full-stack capabilities
📊 Quantify your mentoring experience: 'Mentored 3 junior developers, reducing code review cycles by 40%'
🌐 Highlight any defence, government or secure systems experience as this role operates in national security
Suggested CV bullets
3 bullets our AI drafted for this specific advert, mirroring its ATS keywords.
Add these 3 bullets under your most recent experience:
- •Developed secure backend services using C# .NET Core for 15,000+ users, achieving 99.8% uptime in regulated financial environment
- •Led React frontend development for critical communications platform, reducing user response time by 35% through optimised state management
- •Mentored 4 junior engineers in agile practices and secure coding standards, resulting in 50% reduction in security vulnerabilities
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Letter preview — tailored to FDM Group
Dear Hiring Manager,
FDM Group's Senior Software Engineer position combines my passion for secure systems development with the opportunity to work on critical defence communications platforms. My extensive experience in C# .NET backend development and React frontend work aligns perfectly with your technical requirements for this national security role.
My background in developing production-ready applications in regulated environments has equipped me with the security-first mindset essential for defence sector work. I have successfully mentored development teams whilst contributing to technical architecture decisions, demonstrating the senior-level autonomy this position requires.
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Interview questions
10 questions generated from this advert.
Technical
- ›How would you design a secure communication system using C# and .NET?
- ›Explain your approach to building scalable backend services in a regulated environment
- ›How do you ensure security when developing applications handling sensitive data?
- ›Describe your experience with React state management in complex applications
- ›What strategies do you use for maintaining code quality in agile environments?
Behavioural
- ›Tell me about a time you mentored a junior developer through a complex technical challenge
- ›Describe a situation where you had to work with high autonomy on a critical project
- ›How do you handle working in a secure environment with strict protocols?
- ›Give an example of when you contributed to technical direction in a team
- ›Tell me about a time you had to collaborate with stakeholders on technical requirements
STAR answer examples
Model answers using the Situation-Task-Action-Result framework. Adapt to your own experience.
Tell me about a time you mentored a junior developer through a complex technical challenge
Describe a situation where you had to work with high autonomy on a critical project