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RoofStacks
$106k - $114k estimated
Senior Backend Developer (Card Payment Systems)
İstanbul
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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Is Kotlin a good career?
Yes, Kotlin is a good career choice for developers who want to work in the Android app development, backend development, or cross-platform development space
Kotlin is a modern programming language that was designed to improve upon some of the shortcomings of Java, making it more concise, safe, and interoperable with other languages
Here are some reasons why Kotlin is a good career choice:
- High Demand: Kotlin is in high demand in the technology industry, especially in the Android app development space. Many companies are now using Kotlin to develop their Android apps, and the demand for Kotlin developers is growing rapidly.
- Compatibility: Kotlin is interoperable with Java, which means that developers can use both languages in the same project. This makes it easy for developers to migrate from Java to Kotlin and vice versa, and it also makes it easier to integrate Kotlin into existing Java-based projects.
- Easy to Learn: Kotlin is relatively easy to learn for developers who are already familiar with Java or other similar programming languages. Kotlin has a simpler syntax than Java, making it easier to read and write code.
- Concise and Safe: Kotlin is a more concise language than Java, which means that developers can write less code to achieve the same functionality. Additionally, Kotlin has built-in null safety features that help developers avoid common errors and bugs.
- Career Growth: Kotlin is a relatively new language, which means that there is a lot of room for growth and innovation. Developers who are proficient in Kotlin have the opportunity to contribute to the development of the language and its ecosystem, which can lead to career growth and advancement.