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Süleyman Kayabaşı

@sleymankayaba

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Senior Backend Engineer at Bilyoner who built a random coupon generator that contributed to a 20% engagement uplift.

Turkey

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At Bilyoner, I owned backend delivery for the User Interaction domain: a distributed system of 12 microservices on a platform serving 2.3M+ monthly users. I built the Shake & Win random coupon generator, contributing to a 20% uplift in user engagement after release.

I also led Java 21 and Spring Boot 3.5 upgrades across those microservices and increased unit test coverage from 30% to 80%. For Spor Toto, I extended coupon management with save, edit, and delete flows, attracting 1,500+ new users in the first week.

At n11, I worked across Kotlin/WebFlux microservices and a legacy monolith, migrating payment modules to reactive services handling 125K–150K daily transactions. I maintained zero downtime during Black Friday peak traffic and supported 16 payment methods.

Experience

Work history, roles, and key accomplishments

Senior Backend Engineer

Bilyoner

Dec 2024 - Apr 2026 (1 year 4 months)

Owned end-to-end backend delivery for the User Interaction domain, a distributed system of 12 microservices, serving 2.3M+ monthly users. Led Java 21 and Spring Boot 3.5 upgrades, designed a coupon generator algorithm boosting engagement by 20%, and increased test coverage from 30% to 80%.

Java Kotlin Spring Boot Webflux Cassandra Oracle Elasticsearch SonarQube REST APIs Microservices Distributed Systems Cursor ChatGpt Claude

Software Developer Specialist

n11

Dec 2021 - Nov 2024 (2 years 11 months)

Worked on a hybrid architecture of 25+ microservices and a legacy monolith, migrating payment modules to reactive microservices. Engineered reactive payment services handling 125K-150K daily transactions with zero downtime during peak traffic, and reduced financial losses by 2-3% through bug fixes.

Kotlin Webflux Reactor Microservices Payment Systems Jenkins CI CD Unit Testing Mockito Java

Jr Application Engineer

IBTECH

Jul 2021 - Nov 2021 (4 months)

Implemented concurrent processing components using core Java and multithreading for a loan approval system. Refactored legacy components and resolved 50+ SonarQube findings, documenting technical decisions in accordance with banking standards.

Java Multithreading Concurrency SonarQube Refactoring Documentation