Senior Software Engineer, Internal Tools
First seen by Alion on Oct 14, 2026.
**About The Job
**You’ll be joining a high-performing and rapidly expanding team of engineers at one of Denmark’s fastest-growing companies. Together, we’re building and scaling the internal platforms that power our growth—including CRM system, sales tools, and operational software used daily and enabling our commercial organization to operate efficiently at scale as we continue our European expansion.
This is an opportunity to be part of a company that has grown from startup to unicorn at record speed. As we continue to expand into new markets and serve an ever-growing customer base, you’ll work on challenges that come with operating products at scale. You’ll have significant ownership, the freedom to drive technical decisions, and a direct impact on the solutions used by businesses every day. As we grow, so will your opportunities to develop your skills, take on new responsibilities, and help shape the future of commerce across Europe.
What you'll do
- Design and deliver scalable, maintainable, and high-quality solutions that drive business impact
- Enhance and evolve core internal systems to improve reliability, performance, and user experience
- Continuously optimize CI/CD pipelines and infrastructure to accelerate delivery and increase stability
- Collaborate closely with internal stakeholders to shape ideas, define requirements, and turn them into actionable plans
- Lead cross-functional projects from concept to successful delivery
- Mentor and support team members, fostering technical growth and engineering excellence
- Drive architectural improvements and champion best practices to ensure the platform scales for the future
Who you are
- 5+ years of professional software engineering experience
- Strong experience designing and operating distributed systems
- Demonstrated ability to lead technical projects involving multiple engineers and influence architectural decisions
- Experience building scalable backend platforms and APIs
- Comfortable navigating ambiguity with pragmatism and helping shape new products and systems
- Strong communication and collaboration skills
We don't expect experience with every technology listed below. We're looking for engineers who can learn quickly and help us build great products.
**Backend
**
- Java, Spring Boot
- MySQL
- REST APIs & Event-Driven Architecture
- Domain Driven Design
- Docker, AWS
**Frontend
**
- TypeScript
- React
- TanStack Query
- Jest
- Playwright
- i18n
**Platform & Delivery
**
- GitHub Actions
- CI/CD
- AWS ECS
- Observability & Monitoring
- Feature flags
Why Flatpay?
You’ll help build and scale our internal platform, creating tools that empower teams across Flatpay and shape the future of how we operate, and scale our products.
We offer an inclusive environment where engineers are trusted with ownership and encouraged to make an impact. Our engineering teams work together from our Copenhagen office. We believe that close collaboration, quick feedback loops, and solving problems side-by-side help us build better products, move faster, and create a stronger engineering culture. We also provide plenty of perks including free slush ice, an on-site gym, a fully equipped gamer room, and much more. If you are ready to be part of this exciting journey, we would love to hear from you today.
Established in 2022 in Copenhagen with a commitment to transparency, we've streamlined card payments to small and medium-sized businesses. Our innovative pricing model eliminates hidden costs and fees, offering a simple flat rate for all cards with no monthly subscription for our point-of-sale and payment solutions.
Operating in Denmark, Finland, Germany, Italy, France, the United Kingdom, and the Netherlands, we're more than just a service provider; we are your trusted business partner.
We continuously strive to stay ahead of the curve, adapting our solutions to meet our clients' evolving needs. Ready to be part of something extraordinary?