Senior Backend Developer (Card Payment Systems)

At Roofstacks, we’re building innovative financial technologies that power seamless card experiences. We are now looking for a Senior .NET Developer to join our growing Card Payment Systems team. If you're passionate about banking, payments, and high-performance backend development—this opportunity is for you.

🧩 What You’ll Be Doing

You will take part in the full development lifecycle of our card platform, working on mission-critical services used in:

• Card application flows for Debit, Credit, Prepaid, Digital & Commercial cards
• Integrations with KKB/LKS, Decision Support, Analytics Solutions and onboarding systems
• Development of card lifecycle and transaction management services (issuance, renewal, limits, fraud, posting, fee, campaign, extre, DWH etc.)
• Secure integrations with payment schemes (Visa, Mastercard, BKM, CUP, Discover) and EMV scripting/PIN management
• POS ecosystem integrations (TechPOS, Ingenico SDK, CAT transaction flows, parameter distributions)
• Real-time and batch transaction processing with high availability (99.9% uptime) requirements
• Working with ISO 8583 messaging, socket programming, TCP/IP protocols
• Supporting authentication flows via OAuth2, OpenID Connect, JWT/JWS, and 3DS SDK/ACS

✅ What We’re Looking For

• Minimum 5+ years of experience in software development
• Bachelor’s degree in Computer Engineering, Software Engineering, or related field
• Strong experience in C#, .NET Core / .NET Framework
• Solid command of SQL / PL-SQL (Oracle preferred)
• Experience in multi-threaded applications and performance optimization
• Prior banking or fintech experience is highly preferred
• Hands-on with RESTful API, Webhook integrations
• Strong debugging, testing, and system integration skills
• Good command of English is a plus

⚙️ Nice-to-Have Experience

• Experience with other OOP programming languages (such as Java, Python, Kotlin, etc.)
• EMV transaction flow, 3DS 2.x, ACS and GO integration
• Encoding/decoding logic in card-based data formats
• High-performance architecture experience in financial transactions
• Familiarity with scheme compliance (Visa/Mastercard bulletins & updates)
• Experience in distributed system development
• Familiarity with TCP/IP Socket programming, encoding/decoding formats (hex, bcd, ebcdic)
• Understanding of HSM, key management, encryption flows is a plus