Senior Fullstack Software Engineer

Appgate · Core Team · Gothenburg, Sweden

Want to build software where you can see the difference your work makes?

At Appgate, we develop IT security software that helps organizations control access to their applications and infrastructure. We’re looking for a senior fullstack developer with strong C# experience to join our Core team, building the Appgate SDP client with C# and React/TypeScript. You’ll also contribute to the Java REST backend that the same team works on.

We offer a balance that can be hard to find: a company large enough to surround you with experienced engineers, and small enough for your individual contribution to matter. Here, you can take ownership of substantial features and entire subsystems, help shape technical decisions, and follow your work from the first idea through to customers using it. Why Appgate? The people around you make a difference.

At Appgate, you’ll work with colleagues who bring deep experience in software development, networking and security. There are people to learn from, discuss difficult problems with, and help you explore unfamiliar areas.

At the same time, there is room to make your own mark. We value developers who ask questions, suggest improvements and take responsibility for moving things forward. As your knowledge of the product grows, so does your opportunity to influence it.

Appgate is growing, with major customer contracts driving expansion across our engineering teams. We’re also developing new capabilities in areas such as operational technology (OT), helping secure access to industrial systems. Joining now means contributing as those capabilities take shape.

We're also developing AI-related capabilities in Appgate SDP. As a client and controller developer, you may contribute to how these features connect with the rest of the product, bringing new functionality into the applications and services you work on.

Your role in the Core team

The Core team develops the client and controller at the heart of Appgate SDP.

The client is the software users interact with to connect securely. The controller manages the policies and access decisions that determine what they can reach.

This is a fullstack role: your work will span the client, its C# logic and React/TypeScript interface, and the Java REST backend that powers it. You’ll move across this boundary regularly, understanding how a feature connects from backend logic through to what the user sees. 1 Appgate | Core Team We use agentic AI tools as part of our development workflow and continue to explore where they can help us build, test and improve software. You'll have the opportunity to help shape how we use these tools, applying the same engineering judgment and attention to quality that we bring to the rest of our work.

You’ll help us:

• Develop features for the Appgate client, using C#, React/TypeScript and Electron.

• Develop features for the Java REST backend.

• Investigate and resolve problems across applications, operating systems and networks.

• Improve automated testing, developer tooling and build and release workflows.

• Shape technical solutions through design discussions, code reviews and collaboration across teams.

What you bring

You enjoy building software, understanding how things work, and seeing a solution through. You’re comfortable taking initiative, while knowing when to involve others and work through a problem together.

We’re looking for:

• Strong professional experience with C#. • Backend development experience, ideally with Java.

• Experience with, or working knowledge of, React, TypeScript and Electron. • Confidence supporting and debugging software across Windows, macOS and Linux.

• A working understanding of Unix systems. • An interest in writing maintainable code and improving how it is tested and delivered.

• Good communication skills in English.

Build something, you can put your name to If you’re looking for room to grow, experienced colleagues to learn from, and the opportunity to take meaningful ownership of a security product, we’d like to hear from you.

Join Appgate’s Core team and help shape what comes next.