Senior Backend Developer (Card Payment Systems)

Roof Stacks

5+ Years | Istanbul, İstanbul, Türkiye (Hybrid) | Full Time | 4 months ago

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Job Summary

Roofstacks is seeking a Senior .NET Developer to join their Card Payment Systems team, focusing on building innovative financial technologies for seamless card experiences. The role involves full lifecycle development of card platform services, including debit, credit, prepaid, digital, and commercial cards. Responsibilities include integrations with KKB/LKS, decision support, analytics solutions, and onboarding systems. You will also develop card lifecycle and transaction management services, secure integrations with payment schemes like Visa and Mastercard, and POS ecosystem integrations. The role requires working with ISO 8583 messaging, socket programming, TCP/IP protocols, and supporting authentication flows via OAuth2, OpenID Connect, JWT/JWS, and 3DS SDK/ACS, while maintaining high availability requirements.

Must Have

5+ years of software development experience
Bachelor's degree in Computer Engineering or related field
Strong C#, .NET Core / .NET Framework experience
Solid SQL / PL-SQL command (Oracle preferred)
Experience in multi-threaded applications
Performance optimization experience
Hands-on with RESTful API, Webhook integrations
Strong debugging, testing, and system integration skills

Good to Have

Prior banking or fintech experience
Experience with other OOP languages (Java, Python, Kotlin)
EMV transaction flow, 3DS 2.x, ACS and GO integration
High-performance architecture in financial transactions
Familiarity with scheme compliance
Experience in distributed system development
Familiarity with TCP/IP Socket programming
Understanding of HSM, key management, encryption flows

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

13 Skills Required For This Role

Problem Solving Oracle Talent Acquisition C# .net Core Jwt Openid Connect Restful Api Kotlin Python Sql Socket Programming Java

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