Sefa Karabaş

Contributed as a Full-Stack Engineer on Udemy's Assessment Team, building assessment experiences for a platform serving over 80 million learners worldwide.

• Developed the Google-style Practice Test feature as part of the Grow with Google partnership
• Designed and implemented Domain Assessments, expanding the platform beyond full assessments for learners globally
• Refactored core components to a Hexagonal Architecture, improving maintainability and extensibility
• Contributed to the evolution from a monolithic architecture to microservices and microfrontends
• Contributed to the development of the unified e-learning platform following Coursera's acquisition of Udemy
• Leveraged AI-assisted development, primarily using Claude Code, as part of an agentic software development workflow

Tech Stack: Kotlin, Django, React.js, GraphQL, gRPC, Amazon DynamoDB, MySQL, Datadog, Sentry, Claude Code

Contributed as a Full-Stack Developer, building secure and scalable payment infrastructure for Turkish Airlines' financial systems.

• Developed a Payment Facilitator (PF) service processing 200M+ TRY in daily payment volume with high reliability and scalability
• Led the integration of the Merchant Registration System (İKS), streamlining merchant onboarding processes
• Developed and maintained reconciliation and settlement modules to ensure accurate and reliable financial operations
• Integrated with multiple banking and payment partners, including Payten, Kuveyt Türk, and QNB, to support end-to-end payment flows

Tech Stack: Java, Spring Boot, React.js, Docker, Kafka, CI/CD

Contributed as a Full-Stack Developer on the Payments Team, building secure and scalable payment infrastructure for global social platforms serving tens of millions of users.

• Integrated global payment providers, including Rapyd, Payermax, and Wise, enabling secure and seamless payment transactions
• Developed and optimized pay-in and cash-out workflows to improve the reliability and efficiency of payment operations
• Collaborated with cross-functional teams to deliver scalable payment solutions for high-volume financial transactions

Tech Stack: Django, Vue.js, Node.js, Docker, Jenkins, CI/CD, AWS, Cloud Firestore, Testing

Contributed as a Software Engineer on the Digital Channels & Insurance Team at Yapı Kredi, developing customer-facing banking solutions.

• Developed and maintained backend services using Java and Spring Boot
• Delivered digital banking features in collaboration with cross-functional teams
• Contributed to the development of secure and reliable financial applications

Tech Stack: Java, Spring Boot

Contributed to the Data Warehouse (DWH) project at Odeabank, supporting commercial banking operations.

• Designed and implemented ETL processes using Oracle Data Integrator (ODI)
• Developed and optimized SQL queries on Oracle and MS SQL Server
• Built and maintained reliable data pipelines to support business reporting and analytics

Tech Stack: Oracle SQL, MS SQL Server, ODI

Contributed as a part-time Full-Stack Developer, building both customer-facing and internal management applications.

• Designed and developed the main application and management system from end to end
• Integrated the Paycell payment gateway to enable secure online payments
• Built scalable full-stack solutions tailored to business needs

Tech Stack: Angular, React.js, Redux, Java Spring, Hibernate