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