Senior Software Engineer (AI)

Working Model: Hybrid Working or Remote

Employment Status: Full-time, Permanent

Working hours: Monday to Friday

Office Location: Sofia, Bulgaria

Reporting to: Head of Engineering, UK

Picture yourself at the cutting edge of payments innovation, where each project has the potential to transform the industry. We’re on a dynamic path to redefine what’s possible, with a powerful portfolio that’s set to surpass the competition and position us as a global leader. This is your chance to join us at a pivotal moment in our journey—where your work can make an extraordinary impact.

If you’ve ever dreamed of being part of something remarkable from the beginning, this is your opportunity. As we grow, your role will shape the future, impact customers worldwide, and drive us toward becoming a game-changer in payments. Join us, and let’s create something truly groundbreaking together.

In this role you will add value to PXP by: 

As a Senior Software Engineer at PXP, you’ll play a key role in developing and maintaining the technology that powers our payment platform. This is a hands-on, collaborative position where you’ll work closely with cross-functional teams to design, build, and refine high-performance applications in a fast-paced, agile environment.

While your day-to-day focus will be on our core backend systems, we are looking for an engineer with a strong structural understanding of AI agent orchestration. Your familiarity with how automated agent systems execute tasks, manage state, and call external tools will help ensure our platform’s foundational code is built to seamlessly support and interact with these modern AI workflows.

A typical week might involve:       

Designing, developing, and maintaining core payment software applications on the PXP platform.

Implementing high-quality, maintainable code using C# .NET Framework (and transitioning to C# .NET Core) ensuring that systems are structured cleanly to act as deterministic tools for future AI orchestration layers.

Creating and maintaining SQL Server stored procedures, optimized for a heavily multithreaded and highly concurrent environment.

Collaborating with teams to gather requirements and define technical solutions across our broader ecosystem.

Writing unit tests, leveraging TDD/BDD principles, and conducting code reviews to maintain high-quality engineering standards.

Actively participating in agile ceremonies, including sprint planning, retrospectives, and daily stand-ups.

Tracking industry trends and emerging technologies, specifically noticing how modern enterprise software structures integrate with agentic AI ecosystems

We are looking for someone who:

Bachelor’s degree in Computer Science or a related field.

Solid hands-on experience with C# .NET Framework (and/or .NET Core) and SQL Server.

Strong familiarity with design patterns and flow-based processing. Crucially, you possess a solid conceptual understanding of AI agent orchestration (state machines, loop handling, tool-calling boundaries) rather than just basic prompt generation.

Strong understanding of TDD and BDD principles, with experience using tools like SpecFlow.

Experience with Git and a solid understanding of the Gitflow workflow.

Excellent problem-solving abilities and strong communication skills.

We would love someone to have any of the following:

Online payments and financial systems

Understanding of the challenges in an enterprise, multi-server, multithreading information system

What we can offer you:

You will be joining us at a pivotal moment, where your contributions will directly shape our growth and future success, setting you on the ground floor of something extraordinary.

At PXP, we don’t just offer a job—we offer an opportunity to build something extraordinary. You’ll work on transformative projects, collaborate with passionate colleagues, and see the tangible impact of your efforts on our journey to becoming a global payments leader.

Growth Opportunities: Be part of a company with an ambitious vision, where your role evolves as the company grows.

Cutting-Edge Environment: Work with the latest tools and technologies to drive innovation in the payments industry.

Collaborative Culture: Join a supportive team that values creativity, collaboration, and shared success.

Flexibility: Benefit from hybrid or remote working options that allow you to balance professional and personal priorities, depending on your location.

Competitive Package: Enjoy a competitive salary, performance bonuses, and a range of benefits tailored to your location.

Impactful Work: Play a critical role in shaping the future of payments and making a difference for customers worldwide.

About us:

PXP is a well-established and respected name within the card payment industry.

We boast an impressive and diverse client database across the globe and have over 30 years of experience within the payments space.

Our people are employed across our regional offices located in the UK, Austria, Bulgaria, India and the US.

PXP are a leading payment provider with a reputation for a reliable payment and acquiring platform, as well as offering operational excellence and best-in-class service for all of our clients.

Take your career to the next level and join us as we redefine the payments industry. With our CARE values at the core of everything we do, let’s innovate together.

CARE: Customer at our Core, Accountability, Respect, and Excellence. 

These principles guide everything we do, from how we interact with our customers to how we support one another as a team.