Senior Full-Stack Engineer

Senior Full-Stack Engineer

Bruxelles, Brussels, Belgium

€

6000 - 8500

32 - 40 hours

Build software differently with AI at the core

Software engineering is changing. At HeadFirst x Impellam, we are building an AI-native engineering organization where AI is becoming an integral part of how we design, build, test, and improve software.

As a Senior Full Stack Engineer, you will work across our .NET and Angular platforms and take ownership of complex features from technical design through to production.

You will still be the engineer responsible for what goes into production. The difference lies in how you get there. Tools such as Claude Code and Cursor help you investigate problems, write code, test ideas, refactor, and document solutions more quickly. Your job is to provide these tools with the right context, evaluate their output, and ensure that 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 entire stack and take ownership of the solutions you build.

Your responsibilities will include:

• Building end-to-end features using C#, .NET, ASP.NET Core, Angular, and TypeScript.

• Using AI coding agents as part of your daily engineering workflow.

• Providing AI agents with clear context, constraints, and technical guidance so they can contribute effectively.

• Reviewing AI-generated code and challenging it where necessary in terms of architecture, security, performance, maintainability, and testability.

• Designing and developing APIs, domain logic, data access layers, and integrations.

• Building user-facing experiences in collaboration with Product and Design.

• Improving existing code and reducing technical debt as part of the normal development process.

• Writing meaningful unit, integration, and end-to-end tests.

• Contributing to architectural decisions regarding scalability, reliability, and expansion into multiple markets.

• Sharing knowledge and helping the broader engineering team improve their skills in working with AI.

What does "senior" mean in this context?

For us, seniority isn't about how fast you can type or how much code you can write.

It's a matter of judgment.

You know how to examine a solution and ask the right questions:

• Does this fit the architecture?
• Are the assumptions actually correct?
• Is the security model sound?
• Will we still be able to keep this up in two years?
• Do the tests verify the correct behavior?
• Is there a simpler way to solve the problem?
• Did we provide the AI agent with enough context to make a good decision?

Whether you wrote the code yourself or an AI agent handled most of the implementation, you remain responsible for the result.

Here’s what we offer you

• Salary that matches your experience
• You will receive a salary range that matches your knowledge and experience. We reward you fairly for your commitment and development.
• Vacation pay and days off
• You will receive 8.33% vacation pay and are entitled to 27 vacation days per year based on full-time employment. This gives you plenty of time to recharge your batteries.
• Hybrid working
• We support hybrid working and apply a 60/40 split, whereby full-time employees spend three days at the office and two days working from home.
• Premium‑free pension
• We pay your entire pension premium. This means you accrue pension without having to contribute to it yourself. As a result, you are left with a higher net salary.
• Performance bonus
• Depending on your performance and that of HeadFirst Group, you may receive an annual bonus of one or two months' salary.
• Monthly extras
• You will receive a monthly allowance for internet, a vitality budget, a contribution towards lunch, and support in setting up your home office.

What we expect from you

Who You Are

You are an experienced engineer who enjoys solving complex problems and is committed to building things the right way.

You probably recognize yourself in the following:

• You have 7+ years of professional software engineering experience.