Senior Full Stack Engineer
Summary
Sans Souci is seeking a Senior Full Stack Engineer in Belfast to design and deploy cloud-native web applications, data platforms, and AI-enabled solutions. The role involves working with React, Node.js/FastAPI, and cloud services like Azure or AWS to build scalable products while mentoring team members.
Sans Souci is a fast-growing digital innovation firm based in Belfast. We are looking for a Senior Full Stack Engineer to join our growing technology team and take on real ownership across our client and product work.
We build increasingly sophisticated digital products, data platforms, AI-enabled solutions and cloud services for clients across the public and private sectors. We need you to do more than take tickets and write code. You’ll need to understand a problem, help shape the solution, make sound technical decisions, build it, test it, deploy it, and support other engineers to deliver well. This is a genuine next step for a Senior Developer ready to grow. There is a clear and fast route to Technical Lead for the right person once you've proven your impact.
Location requirement: This role is open to candidates based in Northern Ireland only.
KEY RESPONSIBILITIES:
Software Delivery
- Design, build, and deploy full-stack web applications and APIs
- Work across cloud-native architectures on Azure and/or AWS, including serverless and container-based services
- Contribute to data platforms, workflow orchestration and business process automation
- Apply automated testing, CI/CD and secure development practices throughout delivery
- Support infrastructure-as-code and deployment pipelines across client and internal projects
- Work with the Test Functions to get products release through environments
AI-Enabled Engineering
- Build and support AI and agentic AI solutions, including LLM APIs and RAG architectures
- Work with tool/function calling, structured outputs and vector databases
- Use modern AI-assisted development tools while maintaining engineering discipline, review and testing
- Evaluate and test AI systems for reliability and accuracy
- Stay current with emerging AI engineering practices and bring them into delivery
- Turn incomplete or evolving requirements into sensible technical solutions
- Explain technical decisions clearly to non-technical stakeholders
- Review other engineers' code and share knowledge generously
- Work directly with clients when required
- Support the wider team in raising engineering standards day to day
ESSENTIAL SKILLS & EXPERIENCE
- React, Next.js or similar modern frontend frameworks
- FastAPI, Node.js or equivalent backend technologies
- REST APIs and API-first development
- SQL and modern data platforms
- Cloud & Engineering Practices
- Azure and/or AWS, including Azure Functions / Durable Functions and serverless architectures
- Containers and Docker
- Git and GitHub
- CI/CD and automated deployment; Infrastructure as Code
- Automated testing and application security / secure development practices
You don’t need to tick every box — we are more interested in excellent engineering fundamentals, strong problem-solving ability and the appetite to learn.
DESIRABLE
- Experience with LLM APIs, RAG architectures or AI agents
- Exposure to Azure AI / OpenAI / AWS AI services
- Experience with evaluation and testing of AI systems
- Comfort reviewing others' code or supporting less experienced engineers
- Interest in eventually moving into a broader technical leadership role
WHY JOIN US
- Work with modern cloud and AI technologies
- Influence technical decisions and engineering practices as you grow
- Experiment with emerging technologies
- Work directly with experienced engineers, colleagues and client teams
- See the software you build solve real-world problems
- Progress quickly to Technical Lead as you prove your impact
Salary: £55,000 annually.
If you’re a strong software engineer who wants more ownership, more variety, and room to grow quickly, we’d like to hear from you.