Frontend Engineer (Checkout Team) to Kustom

Kustom; Stockholms kommun; On-site; SEK 750,000 - 900,000; Full time

Benefits offered by this job

Pension plan (national + occupational)

Comprehensive health insurance

Long-term illness protection

Flexible salary exchange options

Annual wellness allowance 3000 SEK

Extra day off for major holidays

Job summary

Kustom, Stockholm-based, invites a Frontend Engineer to shape checkout experiences and contribute to the Morpheus UI library. You’ll own performance, reliability, and observability of frontend code, while mentoring peers and guiding frontend direction.

The role requires strong React skills, a solid UI foundation, and collaboration across teams in fintech/e-commerce domains. Start date is flexible, with full-time 100% capacity in Stockholm.

Qualifications

• Bachelor’s degree in Computer Science, Engineering or similar.
• Strong experience working with React.
• Solid foundation in HTLM, CSS and responsive, accessible UI.
• Experience integrating with backend APIs and dataflows.
• Previous experience building web applications that operates different markets.
• Familiar with iframe and cross-origin integration patterns.
• Experience from fintech, e-commerce, SaaS or consulting environments.

Responsibilities

• Frontend development of checkout products, from full user experience to embeddable components.
• Contribute to the UI library and shared design language.
• Own the performance, reliability, and observability of code for business critical applications.
• Work with testing, security and foster best practises in the team.
• Mentor other engineers, review code and contribute to the technical direction of the frontend.

Skills

React

HTML

CSS

Accessibility

Testing

Security

Code reviews

Mentoring

Education

Bachelor’s degree in Computer Science, Engineering or similar

Job description

Do you thrive on tackling complex challenges? Are you passionate about creating impactful solutions that drive commerce forward? Do you believe in encouraging and elevating those around you? Then this position as Frontend Engineer might be something for you!

About Kustom

Kustom, formerly known as Klarna Checkout (KCO), is the Nordic market leader in digital checkout solutions. Today, they support over 24,000 merchants across more than 170 countries, providing a streamlined checkout experience. They offer localized solutions in 18 markets, tailored to specific languages, currencies, and payment methods. No matter where businesses operate, they deliver a checkout experience that meets the needs of both merchants and shoppers – driving growth globally.

About the position

In this role, you will develop and evolve Kustom’s checkout products, from the complete checkout experience to embeddable components that integrate into a wide range of online stores. You will also play an important role in developing Kustom’s UI library, Morpheus, and the shared design language that brings Kustom’s products together. The role comes with significant responsibility for the performance, reliability, and observability of business-critical code, while also promoting best practices in testing, accessibility, and security. You will contribute to the team’s technical direction through code reviews, mentoring, and close collaboration with other engineers.

As a key member in the Checkout team, you’ll be at the forefront of crafting exceptional digital experiences. We’re not just looking for someone to write code – we’re seeking a creative problem-solver who can transform ideas into intuitive, cutting‑edge interfaces for Kustom’s users. Your expertise will help shape the future of their products, making complex flows feel effortless.

Your main responsibilities:

• Frontend development of checkout products, from full user experience to embeddable components.
• Contribute to the UI library and shared design language.
• Own the performance, reliability, and observability of code for business critical applications.
• Work with testing, security and foster best practises in the team.
• Mentor other engineers, review code and contribute to the technical direction of the frontend.

About you

As a person, we believe that you have strong communication skills and thrive in a business oriented, dynamic environment. You enjoy working independently at times, but also enjoy collaborating with rest of the team. You are fluent in English and are able to work from Kustom’s Stockholm office.

Important for the position

• Bachelor’s degree in Computer Science, Engineering or similar.
• Strong experience working with React.
• Solid foundation in HTLM, CSS and responsive, accessible UI.
• Experience integrating with backend APIs and dataflows.
• Previous experience building web applications that operates different markets.
• Familiar with iframe and cross‑origin integration patterns.
• Experience from fintech, e‑commerce, SaaS or consulting environments.

Kustom’s offer

At Kustom, you’ll have the opportunity to make a real impact on their users’ daily interactions. If you’re passionate about creating high‑performance web applications and thrive on turning ambitious design concepts into reality, we want to hear from you.

Kustom offers a competitive benefits package designed to support both your financial security and overall wellbeing. This includes a comprehensive pension package with both national and occupational pension contributions, extensive health insurance, long‑term illness protection, and flexible salary exchange options. Employees also receive an annual wellness allowance of 3,000 SEK to support activities that keep them healthy and energized. In addition, you get an extra day off when major holidays, such as Christmas Eve or New Year’s Eve, fall on a weekend.

Start: as agreed upon.

Extent: full time, 100%.

Location: Stockholm.

Salary: as agreed upon.