Tolunay Esergün

Backend .NET Developer – Dias Technology (UTTS / Nationwide Fuel Identification System)
Contributed to UTTS, a mission-critical nationwide platform managing fuel transactions across Türkiye.

• Developed high-performance C#/.NET services processing millions of fuel transactions per day.
• Improved authorization, validation, and compliance modules, significantly increasing system reliability and accuracy.
• Optimized RabbitMQ-based communication, reducing inter-service latency by up to 20%.
• Enhanced real-time monitoring and data-processing pipelines using XML/JSON integrations.
• Delivered secure integrations with government institutions, oil distributors, and hundreds of fuel stations across the country.

Tech Stack: C#, .NET 9, ASP.NET Web API, SQL Server, RabbitMQ, REST, gRPC, SOAP, XML/JSON, GitLab

Backend .NET Developer – Papara (Payments & Banking Operations)
Worked on high-volume financial systems powering Papara’s payment and transaction infrastructure.

• Built backend services handling millions of daily financial operations, improving processing efficiency.
• Reduced payment processing latency by 10–15% through service and workflow optimization.
• Developed compliance-aligned modules ensuring full adherence to banking regulations.
• Improved performance in MongoDB and SQL Server data flows, reducing query times significantly.
• Strengthened reliability of event-driven processes using RabbitMQ.

Tech Stack: C#, .NET 8, Web API, MongoDB, SQL Server, RabbitMQ, REST, gRPC, Azure DevOps

Backend .NET Developer – Nesine (Customer Management & International Expansion)

• Enhanced customer management services, increasing system response speed by ~15%.
• Implemented automation workflows that reduced operational errors by up to 20%.
• Contributed to platform internationalization, adapting systems to local regulations for global markets.
• Optimized PostgreSQL and Redis data operations for faster and more reliable processing.

Tech Stack: C#, .NET Core, ASP.NET MVC, PostgreSQL, Redis, MSSQL, RabbitMQ, REST APIs

Backend .NET Developer – Trendyol (Fulfillment & Logistics Systems)
Developed and optimized backend services powering Trendyol’s high-volume order, inventory, and logistics operations.

• Built C#/.NET services used in millions of daily transactions, supporting order management, inventory tracking, and logistics workflows.
• Automated fulfillment processes, reducing operational errors by up to 30% and increasing processing speed for internal teams.
• Improved order management performance, enabling faster and more accurate responses to customer and seller operations.
• Delivered integration services ensuring seamless communication across hundreds of warehouses, suppliers, and courier partners.
• Enhanced delivery traceability and fulfillment KPIs by optimizing data flows and reducing bottlenecks, improving system responsiveness by 15–20%.
• Collaborated with cross-functional teams to analyze requirements and contributed to features impacting millions of active users.

Full Stack .NET Developer – Nacsoft (Research & Development Department)
Led the end-to-end development of an ML-supported invoice/receipt automation platform from scratch.

• Designed and developed the entire platform from the ground up using .NET Core API and .NET Core MVC.
• Automated manual invoice/receipt processing workflows, reducing employees’ processing time by 40–50%.
• Increased data-entry accuracy by over 30% through ML-supported parsing and validation flows.
• Enabled employees to upload, review, and approve documents 2× faster compared to manual legacy workflows.
• Improved overall operational efficiency by centralizing document management, which reduced back-office workload by up to 25%.
• Implemented EF + SQL Server data structures optimized for performance, accelerating data retrieval by 15–20%.
• Carried out R&D for future microservice migration, gaining hands-on experience with Docker, RabbitMQ, Redis, and MongoDB.

Tech Stack: .NET Core, MVC, Entity Framework, SQL Server, Docker, RabbitMQ, Redis, MongoDB

Freelance .NET Developer

• Delivered customized business management and automation systems for clients across multiple sectors.
• Built SOLID-compliant .NET Core MVC applications using layered architecture.
• Improved business tracking efficiency by over 20% through workflow enhancements.
• Continuously refined products based on client feedback, increasing overall user satisfaction.

Portfolio: https://bionluk.com/storksoft
Tech Stack: .NET Core MVC, SOLID, Layered Architecture, SQL Server

IT Intern – Çanakkale Onsekiz Mart University
Supported IT operations and contributed to software development and end-user assistance across the department.

• Assisted academic staff and administrative teams by resolving 15–25 technical support issues weekly, increasing overall IT responsiveness.
• Supported hardware setup and maintenance tasks, helping reduce average troubleshooting time by nearly 10 minutes per device.
• Developed small utility applications that automated simple academic workflows, eliminating dozens of manual steps for users.
• Documented recurring issues and created easy-to-follow guides, reducing repeated support requests by approximately 18% during the internship period.
• Contributed to smoother daily operations by improving communication between staff and the IT team, helping the department handle peak periods with fewer delays.