Senior Fullstack Engineer

Build software differently with AI at the core Software engineering is changing. At HeadFirst x Impellam, we are building an AI-native engineering organisation where AI is becoming a normal part of how we design, build, test and improve software. As a Senior Full Stack Engineer, you will work across our .NET and Angular platform and take ownership of complex capabilities from technical design through to production. You will still be the engineer responsible for what ships. The difference is how you get there. Tools such as Claude Code and Cursor help you investigate problems, write code, test ideas, refactor and document solutions faster. Your job is to give these tools the right context, challenge their output and make sure the final solution is secure, maintainable and fit for purpose. If that sounds more exciting than spending your days manually writing every line of code, keep reading. What you will do You will work across the full stack and have ownership of the solutions you build. Your work will include: Building end-to-end features across C#, .NET, ASP.NET Core, Angular and TypeScript. Using AI coding agents as part of your daily engineering workflow. Giving AI agents clear context, constraints and technical direction so they can contribute effectively. Reviewing AI-generated code and challenging it where needed on architecture, security, performance, maintainability and testability. Designing and evolving APIs, domain logic, data access layers and integrations. Building user-facing experiences together with Product and Design. Improving existing code and reducing technical debt as part of normal delivery. Writing meaningful unit, integration and end-to-end tests. Contributing to architectural decisions around scalability, reliability and multi-market expansion. Sharing knowledge and helping the wider engineering team get better at working with AI. What does senior mean here? For us, seniority is not about how quickly you can type or how much code you can produce. It is about judgement. You know how to look at a solution and ask the questions that matter: Does this fit the architecture? Are the assumptions actually correct? Is the security model sound? Will we still be able to maintain this in two years? Do the tests prove the right behaviour? Is there a simpler way to solve the problem? Did we give the AI agent enough context to make a good decision? Whether you wrote the code yourself or an AI agent did most of the implementation, you remain accountable for the result. Who you are You are an experienced engineer who enjoys solving complex problems and cares about building things properly. You probably recognise yourself in the following: You have 7+ years of professional software engineering experience. You have strong experience with C#, .NET and ASP.NET Core. You have recent hands-on experience with Angular and TypeScript. You are comfortable working with Entity Framework Core and relational databases. You have experience designing secure and maintainable REST APIs. Testing is a normal part of how you work, not something added at the end. You have experience building and running cloud-based applications. You are a strong debugger and enjoy getting to the root of a problem. You can quickly understand an existing codebase and start making a meaningful contribution. You are comfortable challenging technical decisions when you believe there is a better solution. You actively use AI coding tools such as Claude Code, Cursor, GitHub Copilot or similar tools in your day-to-day work. Our technology You will work with a modern Microsoft and Azure based technology stack: Backend: C#, .NET 9+, ASP.NET Core, Entity Framework Core, REST APIs Frontend: Angular 20+, TypeScript Testing: NUnit, Cypress Cloud: Azure App Services, Container Apps, Functions, Cosmos DB, Azure SQL Infrastructure: Docker, Docker Compose CI/CD: Azure DevOps Pipelines, GitHub Actions AI development: Claude Code, Cursor Experience with Domain-Driven Design, CQRS, distributed systems or event-driven architecture is a plus. So is experience with multi-region or regulated platforms and Azure services such as App Configuration. We are also interested in engineers who have thought about how to work effectively with AI agents, for example by structuring specifications, documentation, prompts or reusable context. Why this role? This is an opportunity to be part of an engineering organisation that is actively changing how software is built. You will have the technical depth of a modern .NET and Angular environment, combined with the opportunity to work differently through AI-assisted engineering. Rather than replacing engineering judgement, AI gives you more time to focus on architecture, problem-solving and building the right solution. You will have real ownership over what you build, work closely with Product and Design and contribute to how the wider engineering team adopts agentic software development. If you want to spend less time manually producing code and more time thinking about what should be built, why it should be built that way and whether it is actually the right solution, this could be a great fit. Because when an AI agent gives you a polished implementation, the first question should not be "Does it compile?" It should be: "Is this the right solution?"