Rafet Ersoy Backend Developer
Volume XXV
May — 2026
Konya — Türkiye 37°52′N   32°29′E
N° 01 · Backend Developer

I build robust, high-performance backend systems in Java & Spring Boot.

Backend developer working from Konya, Türkiye. Currently at DefineX, building Spring Boot Batch systems for scheduled data processing and job orchestration.

Selected Work Get in touch
Rafet Ersoy
The Backend
A working notebook by Rafet Ersoy — on systems, batch and the discipline of test coverage.
IssueN° 25–26
FieldBackend Systems
BasedKonya, Türkiye
StackJava · Spring · SQL
Index
§ of works, writings & experiments Rafet Ersoy — backend developer, Konya.
Section 01
About

Code as craft, systems as composition.

I am a backend developer working from Konya, Türkiye, currently at DefineX where I build Spring Boot Batch systems for scheduled data processing and job orchestration. My work sits where reliability matters: payment-adjacent flows, reporting and notification pipelines, the unglamorous and load-bearing parts of a product.

I treat tests as a first-class deliverable. Across three projects I have authored JUnit suites from scratch and pushed coverage past 90%, migrated legacy code to modern Java, and shaved 40% off batch runtime by re-thinking scheduling and I/O. I am happiest when the work is exact and the test report is green.

Section 02
Experience

A short chronology, told plainly.

Jun 2024 — Present

Software Developer DefineX

Designing Spring Boot Batch pipelines for scheduled data processing and job orchestration. Authoring JUnit suites from scratch (90%+ coverage across three projects), migrating legacy code to modern Java, and building notification & reporting services. Optimised batch throughput by 40%.

Java · Spring Boot
Spring Batch · JUnit
PostgreSQL · Docker
2023

IT Intern Düzey — Koç Holding

Built a NopCommerce / .NET e-commerce plugin for internal sales tooling. Learned to ship within a corporate codebase — conventions, code review, release windows.

C# · .NET
NopCommerce
MSSQL
2022

Technology & Innovation Intern Mirsis

Contributed to a TÜBİTAK-supported financial-risk initiative. Wrote Flask REST APIs and worked alongside ML models on prediction tasks. First exposure to taking research code into something a service could call.

Python · Flask
REST APIs
Machine Learning
2019 — 2023

B.Sc. Computer Engineering Sakarya University

Foundations — data structures, operating systems, databases, networks. Where the habit of writing things down precisely was learned.

Education
Sakarya · TR
Section 03
Selected Work

Four pieces — load-bearing, mostly invisible.

N° 01 DefineX · 2024–26 · Case study

Spring Boot Batch — scheduled data processing & orchestration

A family of batch jobs that move records through validation, transformation and downstream notification. Re-thought scheduling and I/O patterns to cut total runtime by 40%.

Read the case study
N° 02 DefineX · Internal

JUnit suites — from scratch, three projects

Wrote unit and integration tests covering services, repositories and batch steps. Crossed the 90% coverage line on each codebase and made the tests fast enough to run on every push.

Coverage · 90%+
N° 03 DefineX · Platform

Notification & reporting services

Service-level work for downstream consumers: scheduled reports, transactional notifications, and the small but exacting work of templating, retries and observability.

Java · Spring · SQL
N° 04 Düzey — Koç · Internship

NopCommerce plugin — .NET e-commerce

A custom plugin extending an enterprise NopCommerce installation. The first time I shipped code inside someone else's release cadence and learned what that costs and pays back.

C# · .NET

Four numbers I keep coming back to.

Section 04 · In figures
As of May 2026
10M
Records processed every night through the batch pipeline
40%
Batch runtime cut by re-thinking scheduling and I/O
90%+
JUnit coverage held in CI across three projects
06
Batch jobs orchestrated, feeding two downstream services
Section 05
Contact
Open to backend & platform roles, contract or full-time.

Write to me, plainly.

info@rafetersoy.com
GitHub github.com/RafetJinx
LinkedIn linkedin.com/in/rafetersoy
HackerRank /pistipist
Located Konya, Türkiye