Senior Full Stack Engineer

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. Please send your CV, LinkedIn profile or GitHub profile along with a short introduction telling us about the type of systems you’ve been building. 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 Collaboration & Client Work • 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 • Python • TypeScript / JavaScript • 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.