Batuhan
Kaş
backend developer
Java · .NET · Node.js
Kocaeli GMT+3
I'm a software developer based in Kocaeli, Türkiye. I wrote webhook integrations in Java and Spring Boot at HepsiJET and a real-time multiplayer games section at SmartWords. These days I work on insurance quote and policy APIs in C# and .NET Core at Doğanium.
Currently at Doğanium Bilgi Teknolojileri.
Scrolling strip. The backend and DevOps tools I use flow into a CI/CD line in the middle, and pipeline steps like tests, Docker builds, Argo CD syncs and rollouts come out the other side.
Experience
08/2026 – present
Doğanium Bilgi Teknolojileri
.NET Developer · Bilişim Vadisi, Kocaeli · on-site
- Developing backend APIs in C# and .NET Core 3.1 for insurance quotation and policy issuance workflows.
- Integrating with external insurance providers' APIs to retrieve quotes based on vehicle and customer information.
- Implementing quotation and policy issuance for multiple products, including traffic, comprehensive auto, short-term traffic and supplementary health insurance.
- Building server-side integrations that streamline quotation and policy processing.
C# · .NET Core 3.1
04/2026 – 08/2026
SmartWords
Full Stack Developer · Bussum, Netherlands · remote
- Added a new Games section to an app with 100K+ downloads. It has live 1v1 duels, daily challenges, a reels-style feed and four leaderboards.
- Built matchmaking on PostgreSQL transactions with advisory locks. Live match state lived in Firestore, and only the backend could write to it.
- Moved scoring to the server. Along the way I found and closed a flaw that counted a malformed request as a correct answer on 99.9% of the game's 3,600 questions.
- Wrote a nickname filter that works in 8 languages. False rejections of real names dropped from 23 of 29 to 0.
PostgreSQL · Firestore
Details: SmartWords10/2024 – 09/2025
HepsiJET
Software Developer · Sancaktepe, Istanbul · hybrid
- Built webhook integrations in JetSuite with Java 11 and Spring Boot. They sent shipment updates to the customer or the company involved, and I tracked shipment status in PostgreSQL.
- Worked full stack on the Courier Management System with Express.js and React. When a ticket touched the backend, the frontend and the database, I made all the changes myself and shipped them together.
- Designed and maintained more than 20 REST API endpoints in Spring Boot and Node.js microservices. Internal apps and external customers both used them.
- Worked in an Agile team of four developers. I took sprint tasks from Jira and delivered them with about 95% test coverage.
- Reworked PostgreSQL schemas for new features and added Redis caching to cut repeated queries on busy endpoints.
Java 8 · Java 11 · Spring Boot · Express.js · React · PostgreSQL · RabbitMQ
Details: HepsiJET
ALSO
- 42 Kocaeli, Tutor Master08/2024 – 09/2024
- 42 Kocaeli, Tutor10/2023 – 11/2023
As a tutor I helped with 42's student selection. I observed the candidates, took notes and wrote assessments of who was doing well and who fit the 42 culture.
Projects
5 projects · on GitHub- 01(opens in a new tab)
Sales Tracking System
An offline point-of-sale app with 32k lines of code and 577 tests that run against a real database instead of mocks. Licenses are signed with Ed25519 and bound to the machine's hardware. Money is handled as BigDecimal, so totals and VAT never pick up floating-point errors. Backups are encrypted with AES-256-GCM.
2026 · Desktop · Java 25 · Swing · SQLite
- 02(opens in a new tab)
Real-Time Multiplayer Game Platform
A team project at 42. I wrote the tournament backend, which builds the bracket, follows each match and moves players to the next round. I also built the auth layer with JWT, two-factor authentication and email-verified sign-up.
2025 · Web · team · TypeScript · Fastify · SQLite · Docker
- 03(opens in a new tab)
Inception of Things
I set up a Kubernetes cluster on K3d (K3s in Docker) and deployed to it with ArgoCD using GitOps. I wrote the Deployment, Service and Ingress manifests.
2025–26 · Infrastructure · K3s · K3d · ArgoCD
- 04(opens in a new tab)
IRC Server
An IRC server that follows RFC 1459 and serves many clients at once. It handles connections, channels and commands with epoll and non-blocking sockets.
2025 · Networking · C++98 · epoll
- 05(opens in a new tab)
Minishell
A Bash-like shell written in C. It runs processes with fork, exec and wait, handles pipes and redirections through file descriptors, and deals with signals and environment variables.
2023–24 · Systems · C · Unix
Other 42 projects:Cub3D (opens in a new tab)Philosophers (opens in a new tab)Inception (opens in a new tab)
About
I live in Kocaeli, Türkiye. I studied computer programming at Kocaeli University. After that I wrote systems and networking projects in C and C++ at 42 Kocaeli, where I also worked as a tutor for a while.
At HepsiJET I worked on integrations in Java and Spring Boot, and on a courier management system in Express.js and React. At SmartWords I built a multiplayer games section for an app with 100K+ downloads. Now I work on insurance integrations at Doğanium's office in Bilişim Vadisi, and I'm studying Management Information Systems at Istanbul University.
I write on Medium about what I'm learning in Kubernetes and CI/CD.
EDUCATION
- 09/2026 – presentIstanbul UniversityManagement Information Systems, bachelor's degree
- 09/2025 – present42 Türkiye, KocaeliRNCP Level 6 (EQF 6, bachelor's equivalent)
- 07/2023 – 08/202542 Türkiye, KocaeliSoftware Development Programme (Common Core)
- 2016 – 2018Kocaeli UniversityComputer Programming, associate degree
AWARD
Best Presentation Award
Bilişim Vadisi Web Technologies Hackathon, December 2025 (opens in a new tab)
LANGUAGES
Turkish (native) · English (B2)
Writing
The articles are in Turkish.- 2026-03-22Bölüm 1: Bare-Metal Sunucularda RKE2 ile Kubernetes Mimarisi ve KurulumuKubernetes · RKE2 (opens in a new tab)
- 2026-01-21GitHub Actions ile İlk CI/CD Pipeline'ımı Nasıl Kurdum?GitHub Actions · Docker (opens in a new tab)
- 2025-12-29Kubernetes'te (K3S) Trafik AkışıK3s · Traefik (opens in a new tab)
Tools
- Languages
- Java · C# · TypeScript · JavaScript
- Backend
- Spring Boot · .NET Core · Node.js (Express, Fastify) · REST · Webhooks
- Data
- PostgreSQL · Redis · Firestore · SQLite · RabbitMQ
- DevOps
- Docker · Kubernetes · GitHub Actions · GitLab CI · ArgoCD
- Frontend
- React
- Tools
- Git · Linux · Jira · Google Cloud