Klarna, based in Stockholm, offers pay-later and other payment options at online and in-store checkouts, along with a shopping app. Its interviews combine coding with system design that leans on payments and risk, and some candidates describe a reasoning or logic test near the start. This page covers what Klarna builds and who it hires, the process candidates commonly report, the technical depth the teams care about, representative problem types, what interviewers score, and a three-week prep plan.
What Klarna builds and who it hires
Klarna built its original payment system in Erlang, and its engineers have spoken publicly about refactoring that system as the company grew quickly. Today its job posts describe back-end platforms in functional languages on the Erlang runtime as well as Java and Scala, deployed on AWS with Docker and Kubernetes, with Kafka, PostgreSQL and DynamoDB in many teams. Engineers work on checkout and payments, credit decisions and risk, the consumer app, merchant tools and the data platform.
- Back-end engineers: payments, credit and merchant services in Java, Scala or Erlang.
- Mobile and front-end engineers: the shopping app and checkout experience.
- Data and machine learning engineers: risk, fraud and personalization.
- Platform engineers: cloud infrastructure and developer tooling.
What the process tends to look like
| Stage | What happens | How to prepare |
|---|---|---|
| Recruiter call and early test | A short recruiter conversation; some candidates also report an online logic or reasoning test | Practise timed reasoning questions if your invitation mentions one |
| Technical screen | A coding challenge that candidates describe in several forms: a HackerRank set of problems from easy to hard, a take-home, or a live session | Practical coding in your interview language, explained aloud |
| Final loop | Live coding or pair programming, a long system design interview, and behavioral and team-fit rounds tied to Klarna's leadership principles | One design in the company's domain and two strong behavioral stories |
Processes differ by team, level and office and change over time, so treat this as the common shape candidates report and confirm the specifics with your recruiter.
Coding, payments design and risk
Design carries real weight. A senior candidate's report describes the system design interview as the longest in the loop, around two hours. Expect to go from requirements to data model to failure handling, and to defend each choice.
Fraud and risk. A natural Klarna design topic is flagging possibly fraudulent transactions in near real time: which signals you score, how you keep latency low at checkout, and what happens when the scoring service is slow.
Functional thinking. Teams that work in Erlang or Scala value immutable data and pure functions. You will not need Erlang to interview, but be ready to talk about why immutability makes concurrent payment code easier to reason about.
Representative problem types
These are the kinds of problems candidates describe, not a leaked question list. Practice the category, not the exact question.
- Design a system that flags suspicious transactions in real time.
- Split a purchase into instalments that sum exactly to the total.
- Design a ticket-sale system that never oversells.
- Implement retries with idempotency for a merchant callback.
- Compute a customer's outstanding balance from payment events.
- Debug or extend existing code in a pair programming session.
- Easy to hard array, string and graph problems in a timed set.
What interviewers score
- Working code: a solution that runs, handles edge cases and is readable by the next engineer.
- Practical judgment: the trade-offs you name and the simplest design that meets the requirement.
- Product sense: understanding who the user is and what failure looks like for them.
- Ownership: examples where you shipped, measured and fixed things yourself.
The behavioral side
Technical rounds decide most outcomes, but every Klarna loop also asks about how you work. Prepare a short story for each of these, with a result and what you learned:
- Something you shipped end to end. Cover the user problem, your decisions, what you measured and what you would change.
- A disagreement with a teammate. Show how you made the decision on evidence and kept the relationship.
- Why this company? Connect its product and engineering problems to the work you want to do next.
Structures and sample answers for the common questions are in our software engineer behavioral answers guide.
A three-week prep plan
- Week 1: practical coding: build small features against an API, parse and transform data, and write tests, in the language you will interview in.
- Week 2: system design for the company's domain, plus two behavioral stories about shipping and fixing something under pressure.
- Week 3: timed mixed problems, a mock interview every other day, and research into the product and its engineering blog.
For practice lists, use LeetCode company-tagged questions; compare the European style of Booking.com and Spotify; and for design rounds, read system design building blocks.
Where CoPilot Interview fits
Most of a Klarna loop is spoken: you explain an approach, defend a trade-off and talk through your past work. CoPilot Interview is an AI interview assistant whose free AI mock interview builds technical and behavioral questions from your résumé and the job description, reads them aloud and scores each spoken answer out of ten, so you can rehearse the explanation as well as the code. The free plan gives 15 minutes a day of live help in sessions of up to 15 minutes, with AI mock interviews included. Online assessments and many coding rounds forbid outside help, so practice beforehand and follow your employer's rules on the day.
Disclosure: CoPilot Interview is our product, so weigh what we say about it accordingly.
Frequently asked questions
What programming language should I use in a Klarna interview?
Use your strongest mainstream language for coding rounds. Many Klarna teams use Java, some use Scala or Erlang, and the job description tells you which.
Does Klarna send an online assessment?
Many candidates report an early online element, either a reasoning test, a timed coding challenge or both, while others go straight to live coding. It changes by office and year, so ask your recruiter.
Do I need to know Erlang to interview at Klarna?
Generally not for coding rounds, which usually let you choose a mainstream language. Teams that hire specifically for Erlang or functional programming will say so in the job description, and for those roles you should expect questions on the language and its concurrency model.
How should I prepare for Klarna coding questions?
Practice practical problems under time limits, build small features against an API in your interview language, and prepare one system design in Klarna's domain. Explain every solution out loud, because follow-up questions about trade-offs matter as much as the first answer.
Can I use AI tools in a Klarna interview?
Only if the instructions you receive say so. Online assessments and live coding rounds generally forbid outside help, and some companies now state their AI policy in the invitation. Use AI to practice beforehand, and follow your employer's rules.
Practice this interview before the real one
The AI mock interview builds questions from your resume and the job description, reads them aloud and scores each spoken answer out of 10. Included on the free plan.
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