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