Abdurrahman Yeşilyurt.
tren

Open to new opportunities

AbdurrahmanYeşilyurt

Role
Backend & Full-Stack Software Developer
Focus
.NET · PostgreSQL · Next.js · React Native
Location
Kocaeli, Türkiye
Languages
Turkish · English (C2)
Military service
Completed

Computer engineer building backend systems with ASP.NET Core, NestJS and PostgreSQL, and web and mobile clients with Next.js and React Native (Expo). Products I have built for companies across several industries are live on the web, the App Store and Google Play; most recently I launched Ecoasistan, my own AI-powered assistant that uses the Claude API to extract appointments, tasks and deadlines from email. I take end-to-end ownership, from API and database design to authentication, cloud deployment and CI/CD automation.

Get in touchGitHub LinkedIn

01

Experience

  1. Present

    Backend & Full-Stack Software Developer

    FreelanceKocaeli / RemoteVarious clients
    • Designed and shipped end-to-end products for companies pursuing digital transformation (see Projects). Built layered Web APIs with ASP.NET Core 8 and NestJS; managed PostgreSQL schemas through EF Core and Prisma migrations and optimized query performance.
    • Implemented JWT and HTTP-only cookie authentication, refresh token rotation with token binding (IP, UserAgent), and role/permission-based multi-tenant authorization; built real-time updates with SignalR/Socket.IO, FCM/APNs and Web Push notifications, and SMTP email integrations.
    • Deployed on Ubuntu servers with Docker, Nginx reverse proxy and SSL; built GitHub Actions CI/CD pipelines covering tests, image publishing, automated deploys, migrations and health checks, with automatic rollback.
    • Built web clients with Next.js, React, TanStack Query and Tailwind CSS, and React Native (Expo) mobile apps live on the App Store and Google Play; set up over-the-air updates with EAS.
    • Prepared DTO contracts and API documentation for frontend teams; diagnosed and fixed production issues from server logs.

  2. Backend Developer

    TOS AnalyticsIstanbulIntern → Part-Time (Remote) → Full-Time (Hybrid)
    • Contributed actively to enterprise-grade Web API development with ASP.NET Core; debugged and refactored code together with team members.
    • Worked on PostgreSQL database design, query optimization, and file management integrations with AWS S3.
    • Participated in version control, pull request reviews, and team-wide code quality efforts on Git; took part in testing Web API endpoints and preparing their documentation.
    • Wrote Python scripts for data processing and analysis tasks; integrated AI tools into workflows to automate processes and improve team productivity.

  3. Engineering Intern

    Kocaeli Metropolitan MunicipalityKocaeli
    • Developed internal-use applications on .NET Framework.
    • Worked on server-side configuration tasks under mentor supervision.
    • Gained hands-on experience in Ubuntu server administration and general system management.

  4. Mobile App Developer

    MERLAB Innovation, Science and TechnologyKonya
    • Built a Flutter mobile application for an industrial weighing system.
    • Integrated sensor data from Bluetooth Low Energy devices into the mobile app.
    • Collaborated with the team on the hardware/software interface.

02

Projects

  • Ecoasistan

    AI · ProductivityWeb

    AI-powered assistant that reads Gmail and Google Calendar and gathers appointments, tasks and deadlines into a single daily feed: calendar suggestions, reply drafts in three tones, an assistant chat and a daily summary notification. Writing to the calendar or sending email only happens with the user’s approval.

    My roleMy own product. The pnpm monorepo architecture (NestJS + Prisma API, Next.js web app, an upcoming Expo mobile app); a classification → extraction pipeline on the Claude API (Zod schema validation, source-quote checks, a tool-less model against prompt injection); rule-based parsers that run before the model; Gmail, Calendar and Outlook integrations; KVKK compliance and automated deploys with Docker and GitHub Actions.

    • NestJS
    • Prisma
    • PostgreSQL
    • Claude API
    • Zod
    • Next.js 16
    • React Native (Expo)
    • Docker
    • GitHub Actions
    Website

  • EcoYazılım

    Business managementWeb + iOS + Android

    Management platform for environmental and occupational-safety consultancies and their client companies: quote and contract approvals, periodic inspection reports, OHS and environmental consulting, an academy, document tracking and carbon report management — plus a mobile app for field teams.

    My roleThe shared ASP.NET Core 8 API behind the Ekonaz products (SignalR notifications, QR-verified PDF reports with QuestPDF, per-company data isolation and permissions) and the Next.js web app; team development on the Expo mobile app; releases with Docker and GitHub Actions.

    • ASP.NET Core 8
    • PostgreSQL
    • SignalR
    • QuestPDF
    • Next.js 15
    • React Native (Expo)
    • Docker
    • GitHub Actions
    Website App Store Google Play

  • Ekonaz Karbon

    SustainabilityWeb + iOS + Android

    Corporate carbon footprint calculation and reporting portal: activity data per facility and period, Scope 1–3 emission calculations, approved PDF reports and a dashboard with charts, based on ISO 14064 and the GHG Protocol.

    My roleThe backend for formula-based emission calculations and the report approval flow (ASP.NET Core 8), the Next.js customer portal and the iOS/Android app built with Expo.

    • ASP.NET Core 8
    • PostgreSQL
    • NCalc
    • QuestPDF
    • Next.js 15
    • React Native (Expo)
    • TanStack Query
    • Recharts
    Website App Store Google Play

  • Sayvera Global

    E-commerce · Direct sellingWeb

    Direct-selling e-commerce platform for natural health and care products: membership and referrals, a team tree with monthly earnings, a seller marketplace and an extensive admin panel.

    My roleMost of the ASP.NET Core 8 backend: layered architecture, the commission engine (binary tree, career ranks), PayTR payments, e-invoice and shipping integrations, scheduled jobs and GitHub Actions deployment.

    • ASP.NET Core 8
    • EF Core
    • PostgreSQL
    • Identity + JWT
    • AWS S3
    • PayTR
    • GitHub Actions
    Website

  • NakliyeKoop

    LogisticsWeb + Android

    Queue and dispatch system for freight cooperatives: vehicle and driver queues, trip tracking and a freight board. Admins run the queue and trips; drivers follow their place in line live from the mobile app.

    My roleThe Flutter mobile app; most of the NestJS backend (JWT, role-based access, real-time updates over Socket.IO, FCM push) and CI/CD deployment on AWS.

    • Flutter
    • NestJS
    • PostgreSQL
    • Socket.IO
    • Firebase (FCM)
    • Docker
    • AWS Lightsail
    • GitHub Actions
    Website Google Play

03

Skills

Core focus

  • 01Backend

    • ASP.NET Core 8
    • .NET 8
    • Entity Framework Core
    • SignalR
    • NestJS
    • Node.js
    • Prisma
    • Socket.IO
    • Web API
    • REST
    • LINQ

  • 02Languages

    • C#
    • TypeScript
    • JavaScript
    • Python
    • Dart
    • SQL

  • 03Databases

    • PostgreSQL
    • Relational data modeling
    • Query optimization
    • Migration management

  • 04Frontend

    • Next.js 15/16
    • React
    • TypeScript
    • TanStack Query
    • Tailwind CSS
    • Astro
    • HTML
    • CSS

  • 05Mobile

    • React Native
    • Expo
    • Flutter

  • 06AI

    • Claude API
    • Zod
    • Structured data extraction with LLMs
    • Prompt-injection-resistant design
    • Model cost tracking

  • 07Identity & Security

    • JWT
    • ASP.NET Core Identity
    • OAuth 2.0
    • Cookie Authentication
    • Refresh token rotation
    • Role- and permission-based authorization
    • Multi-tenant architecture
    • AES-GCM token encryption
    • CSP and security headers

  • 08Integrations

    • Gmail API
    • Google Calendar API
    • Microsoft Graph
    • Firebase Cloud Messaging
    • APNs
    • Web Push
    • PayTR
    • E-invoicing
    • SMTP integrations

  • 09Cloud & DevOps

    • Docker
    • Nginx
    • Ubuntu Server
    • GitHub Actions (CI/CD)
    • Vercel
    • AWS EC2
    • AWS S3
    • AWS Lightsail
    • SSL and domain management

  • 10Tools

    • Git
    • GitHub
    • pnpm
    • Vitest
    • Swagger/OpenAPI
    • Postman
    • Rider
    • Visual Studio
    • VS Code

  • 11Other

    • QuestPDF (PDF generation)
    • NCalc (formula engine)
    • Python for data processing
    • Bluetooth Low Energy integration

05

Writing

All posts

06

Contact

Have a project or an open role? Let’s talk.