Software Developer for Payment integration

Location: Stockholm, Sweden

Duration: 4–6 months (with potential extension)

Start date: As soon as possible

The customer is a global leader in integrated payments, POS, and forecourt automation solutions for convenience retail. Their site controller powers terminals, pumps, payments, and back-office services at more than 10,000 sites worldwide, operating in a mission-critical, always-on environment.

The Role

The customer are seeking an experienced Software Developer to join their established R&D team, focusing on end-to-end payment integrations and implementations aligned with ISO 8583 standard.

Key responsibilities include:

• Develop an ISO 8583 protocol plugin in the existing payment components within the site controller

• Implementing and troubleshooting integrations together with Payment Service Providers (PSPs)

• Integration testing payment flows—from forecourt terminals and devices through to backend services

• Working within a Scrum team, contributing to sprint planning, reviews, and daily stand-ups

• Collaborating closely with QA, product owners, and project managers to deliver high-quality features

Required Experience

• University degree in Computer Science or equivalent experience

• Proven experience with payment integrations using ISO 8583,

• Experience working in agile teams and following modern engineering practices (code reviews, automated testing, CI, Github, )

• C# / Java

Nice to Have

• Experience with device communication, terminals, or embedded/edge systems

• Experience with *Unattended transaction flow Preauthorisation, Amendment, Settlement, Reversal, Reconciliation. *EMV (chip&pin + contactless)

• Experience with or willingness to work in C++

• Spoken and written Swedish

• POS, or regulated environments

Vid intresse, vänligen kontakta moa.ortengren@castra.se