Senior Backend Developer (Card Payment Systems)

Job description

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