Looks like you have JavaScript disabled. For the full Twine experience, you will need to re-enable it.

I am a senior backend engineer with 10+ years in fintech, specializing in modern distributed systems and secure platform design. I have hands-on experience with monolith decomposition, microservices architectures, and event-driven communication for payment and transfer domains. I own production reliability end-to-end, including observability, performance, and security. I am proficient in .NET and Java, message brokers, and SQL/NoSQL datastores, and I actively leverage AI tools to speed up development, refactoring, and troubleshooting in complex systems. I thrive in architecture discussions, guide teams through migrations and modernization, and enjoy delivering scalable fintech platforms with strong security and reliability. I also mentor colleagues, contribute to architectural standards, and continuously seek ways to improve reliability and developer velocity.…I am a senior backend engineer with 10+ years in fintech, specializing in modern distributed systems and secure platform design. I have hands-on experience with monolith decomposition, microservices architectures, and event-driven communication for payment and transfer domains. I own production reliability end-to-end, including observability, performance, and security. I am proficient in .NET and Java, message brokers, and SQL/NoSQL datastores, and I actively leverage AI tools to speed up development, refactoring, and troubleshooting in complex systems. I thrive in architecture discussions, guide teams through migrations and modernization, and enjoy delivering scalable fintech platforms with strong security and reliability. I also mentor colleagues, contribute to architectural standards, and continuously seek ways to improve reliability and developer velocity.

ERSİN TUMAY

Back-End Developer, Full Stack Developer, Web Developer, +4





I am a senior backend engineer with 10+ years in fintech, specializing in modern distributed systems and secure platform design. I have hands-on experience with monolith decomposition, microservices architectures, and event-driven communication for payment and transfer domains. I own production reliability end-to-end, including observability, performance, and security. I am proficient in .NET and Java, message brokers, and SQL/NoSQL datastores, and I actively leverage AI tools to speed up development, refactoring, and troubleshooting in complex systems. I thrive in architecture discussions, guide teams through migrations and modernization, and enjoy delivering scalable fintech platforms with strong security and reliability. I also mentor colleagues, contribute to architectural standards, and continuously seek ways to improve reliability and developer velocity.…I am a senior backend engineer with 10+ years in fintech, specializing in modern distributed systems and secure platform design. I have hands-on experience with monolith decomposition, microservices architectures, and event-driven communication for payment and transfer domains. I own production reliability end-to-end, including observability, performance, and security. I am proficient in .NET and Java, message brokers, and SQL/NoSQL datastores, and I actively leverage AI tools to speed up development, refactoring, and troubleshooting in complex systems. I thrive in architecture discussions, guide teams through migrations and modernization, and enjoy delivering scalable fintech platforms with strong security and reliability. I also mentor colleagues, contribute to architectural standards, and continuously seek ways to improve reliability and developer velocity.

Available to hire

I am a senior backend engineer with 10+ years in fintech, specializing in modern distributed systems and secure platform design. I have hands-on experience with monolith decomposition, microservices architectures, and event-driven communication for payment and transfer domains. I own production reliability end-to-end, including observability, performance, and security. I am proficient in .NET and Java, message brokers, and SQL/NoSQL datastores, and I actively leverage AI tools to speed up development, refactoring, and troubleshooting in complex systems.

I thrive in architecture discussions, guide teams through migrations and modernization, and enjoy delivering scalable fintech platforms with strong security and reliability. I also mentor colleagues, contribute to architectural standards, and continuously seek ways to improve reliability and developer velocity.

Skills

Experience Level

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Expert

Language

Turkish

Fluent

English

Advanced

Work Experience

Senior Software Engineer at Parolapara

August 1, 2025 - Present

Architected and delivered an Open Banking integration platform enabling unified access to Turkish bank account transactions and money transfers. Led microservices transformation for wallet domain, designed secure APIs and scalable integration flows, and implemented event-driven communication with RabbitMQ and OAuth2/OIDC security via Keycloak. Ensured production readiness on Kubernetes with a BFF layer for optimized client interactions.

Senior Software Engineer at Garanti BBVA Bank

December 1, 2024 - July 1, 2025

Developed high-throughput money transfer services (FAST, EFT, Havale) in a microservices architecture handling ~15M transactions/day. Worked across DB2, Oracle, SQL Server, Cassandra, and Elasticsearch; implemented centralized logging and observability improvements. Led a major data migration initiative (15TB DB2→Oracle using ODI) and contributed across the Agile delivery lifecycle.

Senior Software Engineer at Akbank

December 1, 2023 - November 1, 2024

Contributed to ATM platform modernization by migrating legacy ATM flows to a microservices architecture using Java/Spring Boot. Rebuilt critical ATM workflows (QR cash withdrawal/deposit, bill payment, prepaid card flows) and retired mainframe COBOL dependencies to enable agile delivery. Mentored junior engineers to improve code quality and throughput.

Senior Software Engineer at Garanti BBVA Bank

December 1, 2020 - November 1, 2023

Delivered backend solutions for banking domains (lien/haciz, cheque/senet, consumer arbitration) and led legacy modernization from .NET Framework 2.0 to .NET 7. Implemented Elasticsearch to strengthen search and observability, and replaced OCR-based scanning with REST APIs and text parsing for automation. Served as Tech Upgrade Initiative Lead and provided 24/7 production ownership.

Senior Software Developer at INDATA Industrial Data Technologies

January 1, 2020 - November 1, 2020

Contributed to Islamic finance platforms, delivering backend features and data-heavy workflows. Designed financial simulation module, built advanced SQL reporting, supported cloud adoption on Azure, and implemented CI/CD pipelines with Jenkins and Docker for standardised deployments. Developed TÜBİTAK-approved raffle application and automated diverse test suites for release confidence.

Software Developer at Asyasoft Technologies

January 1, 2015 - December 1, 2019

Delivered financial software for tourism, covering billing, accounting, and regulatory compliance with Turkey’s e-government standards (e-Defter, e-Fatura, e-Arşiv). Implemented POS integrations and owned end-to-end delivery including 24/7 production support to ensure reliability of revenue-critical systems.

Software Developer at INDATA Industrial Data Technologies

January 1, 2020 - November 1, 2020

Contributed to interest-free finance (Islamic finance) software platforms, delivering backend features and data-heavy workflows. Designed and implemented a financial simulation module to support scenario-based modeling and analysis for business stakeholders. Built advanced SQL reporting capabilities and optimized complex queries for large datasets, improving accuracy and usability of operational reports. Supported cloud adoption using Azure and developed supporting components with JavaScript where needed. Implemented DevOps practices and integrated CI/CD pipelines using Jenkins; containerized services with Docker to standardize environments and deployments. Developed a raffle application that received TÜBİTAK approval, meeting compliance and audit expectations. Created automated test suites including integration tests, smoke tests, and security-focused tests to improve release confidence.