Frontend Engineer - Checkout Team

Kustom; Stockholms kommun; On-site; SEK 446,400 - 669,600; Full time

Benefits offered by this job

Robust pension plan

Excellent health insurance

Annual wellness allowance of 3,000 SEK

Extra day off for major holidays

Continuous learning opportunities

Job summary

Kustom is looking for a talented Frontend Engineer in Stockholm to join our Checkout Product team. This role is crucial for designing and implementing user interfaces with modern JavaScript frameworks, working closely with designers and backend engineers for a seamless user experience.

As part of a dynamic team, you'll transform creative concepts into functional applications, ensuring high performance and optimal user experience. Join us to make a real impact in the digital checkout solutions space.

Qualifications

• Bachelor's degree in Computer Science, Engineering, or a related field.
• Deep expertise in modern JavaScript and TypeScript.
• Strong experience with React latest versions and knowledge of its patterns.
• Comfort with a modern build setup and willingness to work with build tooling.

Responsibilities

• Design and implement user interfaces using modern JavaScript frameworks.
• Collaborate with designers and backend engineers to deliver engaging web applications.
• Own the performance, reliability, and observability of code for merchant use.

Skills

Modern JavaScript

TypeScript

React

HTML

CSS

Backend API integration

Frontend testing

User Experience (UX)

Education

Bachelor's degree in Computer Science or related field

Tools

Vite

Web Components

Job description

Be a part of the next big thing

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?

About us

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

The role

We are looking to hire a Frontend Engineer to join our Checkout Product team. In this role, you will be responsible for designing and implementing user interfaces using modern JavaScript frameworks. You will work closely with our designers, product managers and backend engineers to deliver seamless and engaging web applications that optimise the user experience and drive conversion.

As a key member of our 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 our users. Your expertise will help shape the future of our products, making complex flows feel effortless.

At Kustom, you'll have the opportunity to make a real impact on our 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.

Our teams are based in Stockholm, where we prioritise in‑person collaboration at our office to foster strong team dynamics.

Things you’ll be doing

• Ship features across our checkout products – from the full checkout experience to the embeddable elements library.
• Contribute to Morpheus (our UI library) and the shared design language that holds these products together.
• Help us evolve our embeddable elements built on Web Components, which merchants integrate into very different storefronts.
• Own the performance, reliability, and observability of code that runs in a business‑critical path for our merchants.
• Champion good practice in testing, accessibility, and security, and help raise the bar across the team.
• Mentor other engineers, review code and contribute to the technical direction of the frontend.

Skills and experience you'll need

• Bachelor's degree in Computer Science, Engineering, or a related field.
• Deep expertise in modern JavaScript and TypeScript.
• Strong experience with React latest versions and a good grasp of its modern patterns.
• Comfort with a modern build setup (we use the latest Vite), and a willingness to dig into build tooling when it's the right lever.
• Solid foundations in HTML, CSS, and responsive, accessible UI.
• Experience integrating with backend APIs and reasoning about async data flow.
• A component‑driven mindset, and experience working with or contributing to a shared design system.
• Experience across the frontend testing spectrum (unit, integration, end‑to‑end) and a good sense of what's worth testing.
• A production mindset of care about real user experience, performance, error rates and observability.
• Strong communication skills and the ability to work effectively in a dynamic environment.

We believe you'll thrive in this role if you have

• Experience building Web Components or other embeddable widgets that have to live inside someone else's site.
• Familiarity with iframe and cross‑origin integration patterns and how to safely run a piece of UI inside another product.
• Experience with localisation and building products that work across many markets and languages.
• A background in payments, e‑commerce, or any domain where conversion is a first‑class metric.
• A genuine interest in User Experience (UX) and how design and engineering decisions shape it.
• Experience with A/B testing and conversion rate optimisation (CRO).
• Experience with web performance optimisation and Core Web Vitals.
• Experience with Agile/Scrum development methodologies.

Benefits

• Robust pension plan with national and occupational components.
• Excellent health insurance coverage, including long‑term illness protection and salary exchange options.
• Annual wellness allowance of 3,000 SEK to invest in your health and fitness.
• Extra day off when major holidays (e.g., Christmas Eve, New Year's Eve) fall on weekends.
• Continuous learning opportunities and professional development support.

A place to grow

At Kustom, you won’t just be another face in the crowd. This is a place where we elevate each other and celebrate success as a team. We believe in our ability to create excellence – and have fun doing it!

We know we set high expectations, but we also know that the road to success isn’t a straight line. We support and encourage each other to try, to fail, to try again. Because that’s how we grow, individually and together.

Does this sound like the place for you?