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.