Junior Kernel Developer – Softpay.io

On behalf of Softpay, TrinityHR are looking for a Junior Kernel Developer for its Client team: the people who build the software that reads the card in every Softpay payment.

We're looking for a recent graduate with a strong technical foundation and a genuine interest in security, cryptography and how payments work.

Softpay is a fintech company based in Copenhagen, founded in 2020, has more than 60 employees and is on an exponential growth journey.

The Softpay Platform turns phones into payment terminals, so merchants can accept in-person payments without extra hardware. The platform is PCI MPoC certified, PCI DSS compliant and PCI PIN compliant. Softpay is working with all the major payment schemes and a range of acquirers, banks and partners to bring it to merchants.

Softpay operates in an international environment characterised by an entrepreneurial and informal culture. Workflows and decision-making processes are fast and unbureaucratic.

Softpay works with several large Danish and international brands and is live in more than 45 countries.

What you'll be working with:

• C++ and Kotlin development on Android
• Cryptography and secure software development
• Payment technologies and card transactions
• NFC, smart cards and embedded systems
• Security-critical software and payment kernels

Your profile

You might have explored cryptography, payments, embedded systems or operating systems in your thesis, built a smart card or microcontroller project at university, or simply developed a strong interest in how secure systems work.

What would make you a great fit?

• A recent BSc or MSc in Computer Science, Software Engineering, or similar
• Programming experience in at least one language - C, C++, Java, Kotlin, etc. C++ experience is a plus
• A strong interest in cryptography and a good theoretical understanding of how it works and is used in practice
• An interest in software security and secure coding
• Fluent in English (Danish is a plus)

Nice to have. It would be an advantage (but not a must) if you:

• Understand the card payment flow (merchant, acquirer, card scheme and issuer)
• Have explored EMV, NFC or smart cards
• Have worked on projects involving AES, RSA or ECC, including key management
• Have experience with C++ or Android
• Have handled untrusted input or sensitive data in a project, or know what PCI or MPoC is
• Have taken embedded or OS courses, or built a microcontroller or hardware project

What makes this opportunity special?

• You don't need years of industry experience. Softpay will provide dedicated training, regular one-to-one mentoring and hands-on experience from day one
• Months 1–3: build and run the kernel, tap test cards, trace a transaction from the SDK call down to the card, and fix your first bugs
• Months 3–6: take small tickets on your own in C++ and Kotlin, and go through a full release with your trainer
• Months 6–12: work independently on kernel tickets, run a release and investigate field issues from the logs as a full member of the kernel team, with opportunities to expand into other native modules over time
• This is a great opportunity to turn your academic knowledge and interest in cryptography into real-world engineering experience – working with technology that powers secure payments
• Work in a fast-growing company in the field of payments and Fintech
• A flat organization and hierarchy model where you can both influence and learn
• Good office location in Copenhagen, that includes an excellent espresso machine!
• A company that is financially backed by a series of entrepreneurs and investors

Practical details

• The role is onsite at Softpay's office in Copenhagen
• Application deadline: We will review applications ongoing, so apply today.
• Contact: Marlene Servé, Partner TrinityHR, [email protected]
• Apply with your CV, grade transcript and a few lines on a project you're proud of