This position is as a full time employee position supporting the financial services/payments space and is fully onsite in Au in der Hallertau, Germany. Please apply only if you have experience with a valid work authorization.

About Blankfactor

At Blankfactor, we are dedicated to engineering impact. We build high-quality tech solutions for companies looking to innovate and grow—especially in fast-moving industries like payments, banking, capital markets, and life sciences.

About the Role:

We are seeking a Senior Android Payments Developer to lead development of card acceptance applications on POS devices and play a significant role in a legacy modernisation programme. You will design and implement robust, secure Android software for terminals (including PAX devices), work closely with QA, product and programme teams, and drive payment certification with major card schemes.

Key Responsibilities:

• Design and implement Android applications for point-of-sale terminals: deliver clean, maintainable Java/Kotlin code that runs on embedded Android and AOSP-based POS devices.
• Integrate with POS hardware: implement and validate drivers and SDK integrations for card readers, PIN pads, NFC/contactless, EMV readers, printers and peripherals (experience with PAX SDKs and device-specific APIs expected).
• Payment flow implementation: author authorisation, settlement, reversal and offline-capable flows; ensure correct handling of EMV, contactless and magnetic stripe scenarios.
• Support payment certification: prepare artefacts, run test suites and co-ordinate certification activities with card schemes and acquirers (Visa, Mastercard, American Express and others); address scheme audit findings and remediation.
• Contribute to legacy transformation: migrate and refactor legacy payment codebases to modern architectures (modularisation, services, secure SDKs), preserving backward compatibility and minimising customer impact.
• Security and compliance: implement secure coding practices, support PCI and terminal security requirements (PCI PTS, EMV kernel considerations), and liaise with security and HSM teams on key management interfaces.
• Performance, reliability and observability: profile and optimise application performance, improve startup times and memory usage, and add telemetry/diagnostics to aid support and SRE teams.
• Automation and CI/CD: build and maintain automated build, test and release pipelines for terminal images and application packages; support automated regression and device farm test runs.
• Defect resolution and production support: drive root-cause analysis for critical incidents, produce fixes and participate in post-release reviews.
• Mentoring and collaboration: review peers’ code, share knowledge across the team, and work closely with QA leads, programme managers and product owners to align delivery priorities.

Primary Objectives:

• Deliver high-quality Android POS applications for multiple device families (including PAX) that meet functional, security and performance targets.
• Successfully complete payment certification cycles with major card schemes and acquirers, achieving approval with minimal rework.
• Advance the legacy transformation programme by migrating key components to modern, maintainable implementations while minimising disruption to services.
• Reduce production defects and incident mean time to resolution through better testing, telemetry and automated checks.
• Ensure software fulfils compliance requirements and is supportable in live environments.

Knowledge & Skills:

• Strong hands-on Android development experience (Java and Kotlin) on embedded/AOSP variants used in POS devices.
• Proven experience with POS device SDKs and hardware integration—experience with PAX devices and SDKs highly desirable.
• Deep understanding of payment terminal flows, EMV transaction lifecycle, contactless/NFC processing and implications for application logic.
• Practical familiarity with payment scheme certification processes and requirements for Visa, Mastercard, American Express (preparing logs, test cases, remediation).
• Awareness of industry security standards: PCI (including PCI PTS) and EMV kernel behaviours; understanding of secure key management concepts and HSM interactions.
• Experience with automated testing and CI/CD for mobile/embedded applications: unit, integration, UI automation and device farm orchestration.
• Proficient with modern development toolchains: Android Studio, Gradle, Git; experience with Jenkins/GitLab CI/Azure DevOps or equivalent.
• Competence in debugging on physical devices, serial/USB/Bluetooth/NFC communications, and analysing logs and traces from constrained environments.
• Strong analytical skills, attention to detail and methodical approach to debugging and problem resolution.
• Effective verbal and written communication; able to prepare technical artefacts for certification, and present technical trade-offs to product and programme stakeholders.
• Experience working in regulated/financial environments (fintech, payments) and in large enterprise delivery contexts.

Educational & Professional Requirements:

• Bachelor’s degree in Computer Science, Engineering or equivalent practical experience.
• Relevant certifications (Android, EMV, PCI or equivalent) are advantageous.
• Demonstrable track record of shipping payment terminal software and participating in card-scheme certification or acquirer testing is highly desirable