Senior Software Engineer, Online

Flatpay; Herlev Kommune; On-site; DKK 900,000 - 1,300,000; Full time

Benefits offered by this job

On-site gym

Gamer room on-site

Free slush ice

Job summary

Flatpay is building the online payments platform and seeks a Senior Software Engineer to define the technical direction and architecture for the online domain. You will help shape how the platform evolves as adoption grows and mentor engineers along the way.

You will design and implement scalable backend systems, APIs, and integrations, while collaborating with product teams to deliver high-impact payment experiences. Join our Copenhagen team and help Flatpay scale globally.

Qualifications

• 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.

Responsibilities

• Design and build scalable systems powering online payments and commerce experiences.
• 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 integrations that enable online payment experiences.
• Improve reliability, observability, performance, and security across the platform.
• Partner with engineers, product managers, and stakeholders to drive technical and product outcomes.
• Mentor engineers through coaching, code reviews, and knowledge sharing.

Skills

7+ years experience

Distributed systems design

Lead technical projects

Backend APIs

Ambiguity navigation

Communication skills

Payments/fintech exposure

Tools

Docker

AWS

TypeScript

React

TanStack Query

Jest

Playwright

GitHub Actions

CI/CD

AWS ECS

Observability

Job description

About the job

Flatpay has become one of the fastest-growing payment companies by helping merchants accept payments in-store. Now we're taking the next step.
Online is one of Flatpay's newest and most strategic engineering domains. We're building the products and platforms that enable merchants to accept payments online and grow their businesses in the digital economy.
As a Senior Software Engineer, you'll play a key role in defining the technical direction of Flatpay's online platform and helping establish the technical and architectural foundations that will support the next phase of Flatpay's growth.
This is a unique opportunity to join at an early stage. While Flatpay already serves merchants at scale, our online platform is still in its early stages. You'll have the opportunity to help launch new solutions, shape how the platform evolves as adoption grows, and learn directly from customers along the way.
If you enjoy building products from the ground up, working close to customers, and seeing your work evolve from first launch to large-scale adoption, you'll have the opportunity to make a significant impact in a domain that will play an important role in Flatpay's future growth.

What you'll do

• Design and build scalable systems that power online payments and commerce experiences




• 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 integrations that enable online payment experiences




• Improve reliability, observability, performance, and security across the platform




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




• Mentor engineers through coaching, code reviews, and knowledge sharing




• Help establish engineering standards and best practices as the Online 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




• Comfortable navigating ambiguity and helping shape new products and systems




• Strong communication and collaboration skills




• Experience within payments, fintech, e-commerce, SaaS, or high-scale transaction systems 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.