About the job

Flatpay has become one of the fastest-growing payment companies by helping merchants accept payments in-store and online. But with 100,000+ merchants relying on us today, payments are only part of running a business — every transaction eventually needs to land in the books, and that's still far too much manual work.

Accounting and Bookkeeping is one of Flatpay's most strategic engineering domains. We're building the products and platforms that turn transaction data into clean books and accurate financial records — including integrations with the accounting systems our merchants already use.

As a Senior Software Engineer, you'll play a key role in defining the technical direction of Flatpay's accounting platform — from how we model financial data, to how we build systems that handle real-world bookkeeping at scale and connect reliably with the third-party systems on the other end.This is an opportunity to join a company that has grown from startup to unicorn at record speed. You'll have significant ownership, the freedom to drive technical decisions, and a direct impact on tools that 100,000+ businesses can rely on. As we expand across markets — each with its own accounting practices, tax rules, and reporting requirements — you'll help shape how Flatpay scales financial infrastructure.

If you care deeply about the accuracy financial data demands, this is a domain where your work will play a central role in Flatpay's future growth.

What you'll do

• Design and build scalable systems that power Flatpay's accounting and bookkeeping capabilities

• Lead feature and platform initiatives involving multiple engineers, driving delivery from discovery through production

• Take ownership of features from design and implementation through deployment and maintenance

• Drive architectural decisions and long-term technical improvements

• Build APIs, services, and data models that handle financial data accurately and at scale

• Improve reliability, observability, performance, and security across the platform — with particular attention to the accuracy and consistency that financial data requires

• Partner with engineers, product managers, and stakeholders to drive technical and product outcomes

• Help establish engineering standards and best practices as the Accounting and Bookkeeping domain continues to grow

Who you are

• 7+ 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, especially ones that integrate with internal and third-party systems

• Comfortable navigating ambiguity and helping shape new products and systems

• Strong communication and collaboration skills

• Experience within payments, accounting and bookkeeping systems, or financial data platforms is a plus

You'll be working with technologies such as the following.

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, feature flags

Platform & Delivery

• GitHub Actions

• CI/CD

• AWS ECS

• Observability & Monitoring

Why Flatpay?

As part of our team, you'll join 2,000+ passionate Flatpayers dedicated to shaping the future of payments.

You'll help build a strategic new business area from the ground up, working on products that directly connect merchants and consumers while shaping the future of online payments at Flatpay. 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're ready to help build and scale the future of payments, we'd love to hear from you.