Lead Engineer Application Security

Klarna; Greater London; On-site; GBP 48,000 - 70,000; Full time

Job summary

Klarna in London is seeking a Lead Engineer for the Secure Development team to help prevent security flaws before they reach production. You will work hands-on with engineering, perform threat modeling and architecture reviews, and drive security improvements across services.

The role emphasizes building tooling, automation, and robust security processes, with opportunities to influence design decisions and mentor engineers across multiple Klarna platforms and countries.

Qualifications

• Experience solving security issues pragmatically with risk-based decisions.
• Ability to break down complex systems and propose practical fixes.
• Experience with web/mobile/security and cryptography is preferred.
• Strong English communication skills.

Responsibilities

• Perform threat modeling and architecture reviews with engineering teams.
• Drive security improvements through active architectural decisions.
• Build and improve Klarna's security tooling, automation, and processes.
• Conduct security assessments including code reviews and pen tests.
• Contribute to Klarna's internal security community.

Skills

Security engineering

Threat modeling

Code review

Penetration testing

English proficiency

Architectural reviews

Communication with engineers

Tools

Java

JavaScript

Python

Go

Erlang

Scala

NodeJS

Cloud

Job description

Salary: £48,000 - 70,000 per year

Requirements:

• We take a pragmatic approach to solving security issues, weighing effort against effect rather than chasing theoretical risk.
• We break down complex systems, spot where theyre likely to fail, and land on fixes that work in practice.
• We have written and reviewed code in at least one of: JavaScript (NodeJS), Python, Go, Erlang, Java, or Scala.
• We are proficient across several of web application security, mobile application security, network security, operating system internals and hardening, applied cryptography, and cloud computing, and we are experts in at least one of them.
• We have working proficiency in English.
• Bonus: experience with BugBounty programs or CTF competitions.
• Bonus: communication skills that hold up when explaining security tradeoffs to engineers who dont work in security day to day.
• We welcome candidates from non-traditional or self-taught security backgrounds.

Responsibilities:

• We perform threat modeling and architecture and design reviews, helping teams design hard-to-break applications and services.
• We take an active role in architectural decisions, working directly with engineering teams to drive security improvements.
• We build and improve Klarnas security tooling, automation, and processes on an ongoing basis.
• We perform security assessments of Klarna services, including code reviews and penetration testing.
• We contribute to Klarnas internal engineering security community.

Technologies:

• Cloud
• Cryptography
• Erlang
• Java
• JavaScript
• LESS
• Mobile
• Network
• NodeJS
• Python
• Scala
• Security
• Web
• AI

More:

At Klarna, we are building an everyday finance network, helping over 120 million consumers across 26 countries save time and money and worry less about their finances. Our Secure Development team equips our engineers to design, build, and deliver secure software through standardized tools and processes, continuous learning, and a security-focused engineering culture. As a Lead Engineer, you will work cross-functionally across our engineering division from Stockholm, London, Milan, or Warsaw, with a focus on preventing security flaws before they reach production. We are looking for someone who enjoys hands-on work, architecture reviews, threat modeling, code review, penetration testing, and building the tooling and automation that make secure practices easier across Klarna.

last updated 37 week of 2026