Senior Software Engineer (Card Present)

We are expanding our Card Present platform, the infrastructure that powers in-person, tap, dip, and swipe transactions at point-of-sale, and are looking for a Senior Engineer who combines deep payments domain expertise with strong backend engineering fundamentals.

Responsibilities

• Design, develop, and maintain backend services that manage communication between payment terminals and our processing infrastructure, supporting EMV chip, NFC/contactless, and magnetic stripe transaction flows.
• Integrate with device management platforms and terminal SDKs including solutions such as Clover, Stripe Terminal, Square, and similar off-the-shelf card present providers, adapting their APIs to fit our platform architecture.
• Implement and maintain device hub capabilities including terminal provisioning, configuration management, firmware coordination, and health monitoring.
• Own and drive EMV Level 3 certification efforts in partnership with payment networks and device vendors, coordinating test plans, managing certification tooling, and resolving certification findings.
• Design and build card-present infrastructure with international markets in mind, accounting for regional EMV implementation differences, multi-currency support, and varying certification requirements across acquiring markets.
• Build scalable, maintainable backend services using .NET and C#, adhering to established architectural patterns and contributing to their evolution.

• Implement robust retry logic, timeout handling, and graceful degradation to ensure transaction integrity even in the presence of network instability or device failures.

• Write secure code that meets PCI DSS requirements across all card-present transaction flows, with a particular focus on cardholder data handling, encryption, and key management.
• Apply point-to-point encryption (P2PE) and tokenization standards correctly within device integration and transaction processing layers.

• Act as a technical resource and mentor for junior and mid-level engineers on the squad, supporting their growth through pair programming, code review feedback, and knowledge sharing.
• Document card-present domain knowledge including certification processes, integration quirks, device-specific behaviors

Qualifications

• Strong proficiency in C# and the .NET ecosystem, with experience building production-grade backend services and APIs.
• Hands-on experience with EMV payment flows including chip, contactless/NFC, and magnetic stripe, ideally including direct involvement in EMV Level 3 certification processes.
• Experience integrating with payment terminal hardware and device management platforms, with an understanding of terminal communication protocols (TLV, ISO 8583, or similar).