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, specialising in the financial-technology domain. I build Spring Boot Batch systems for scheduled data processing and job orchestration, working across large-scale data flows and payment integrations. My work sits where reliability matters — reporting and notification pipelines, the unglamorous and load-bearing parts of a product — and is shaped by data-privacy regulations such as KVKK/GDPR.

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

Won the internship through the Koç Ctrl+ Future Bootcamp. Built a NopCommerce / .NET plugin for stock-based product grouping via paging, and 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-STAR-supported financial-risk initiative — financial-statement analysis and the uniform chart of accounts. Wrote Flask REST APIs for a personality-analysis platform 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

Five products — designed and built end-to-end.

N° 01 Location marketplace · Live

Enyakininda — location-based services marketplace

A modular-monolith Spring Boot platform (Spring Modulith, 23 domains) that surfaces the nearest verified businesses through PostGIS proximity search. Iyzico subscriptions, Supabase-auth JWT, Resend email and FCM push — with a React PWA, an admin panel and a React Native app, behind Cloudflare with R2 media.

Read the case study
N° 02 Laundry SaaS · Live

UMKA Laundry — ops & e-invoice automation

An industrial-laundry management system: order intake, Excel import, packaging and thermal receipt printing. A Uyumsoft integration turns manual e-waybill and e-invoice issuing into an automated lifecycle. Spring Boot + JWT backend, a React panel, Resend email, and an Electron desktop app with silent printing.

Read the case study
N° 03 Hotel SaaS · In development

Guesperia ORMS — guest-request & SLA engine

Guests scan an in-room QR to request items; staff work them against a server-authoritative SLA clock. A multi-tenant, hexagonal Spring Boot service (Java 21) with Redis pub/sub, a ShedLock-guarded SLA ticker, SSE streams and a Next.js panel.

Read the case study
N° 04 Finance SaaS · Live

Fatura Takip — project-based finance tracking

Income, expense and split-payment tracking for agencies and freelancers, with invoiced/uninvoiced separation and monthly P&L. A Next.js app (server actions) over Supabase with heavy in-database logic, Lemon Squeezy billing, Resend notifications and a shareable client portal.

Read the case study
N° 05 Sales intelligence · Live

Sincapsoft Lead Agent — regional lead generation

Scrapes local businesses, scores them on a Pain/Fit/Opportunity model and drives them through a 10-stage CRM. A Next.js command-center over Supabase and n8n workflows, enriched with PageSpeed, Instagram and Claude-analysed reviews across 81 provinces.

Read the case study

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