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Senior Backend Developer (Card Payment Systems)
Ä°stanbul
RoofMoney – Kart Paketi /
Full Time /
Hybrid
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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
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What does a back-end developer in Web3 do?
A back-end developer in web3 typically works on the server-side of a web application, using technologies that are specific to the decentralized web (also known as Web3-related)
This might involve building and maintaining the infrastructure that supports decentralized applications (dApps), or developing the underlying smart contracts and blockchain-based systems that power those dApps
In general, the goal of a back-end developer in web3 is to create the technologies and tools that enable users to interact with the decentralized web in a secure and seamless way.