Mert Celal Yılmaz

• Contributed to backend, frontend, security and integration components of enterprise SaaS platforms in Agile delivery cycles using GitLab and Jira.
• Developed multi-tenant APIs with .NET 9, ASP.NET Core, Clean Architecture and CQRS, creating scalable business rules and reusable REST services.
• Implemented JWT refresh-token flows, HttpOnly/SameSite cookies, RBAC, audit logging and rate limiting, and performed security hardening based on penetration test findings.
• Built real-time notification and permission-propagation mechanisms with SignalR; automated operational processes with scheduled Hangfire jobs.
• Integrated SOAP/REST banking APIs, MutluCell SMS, the 3CX call center API and WhatsApp/WATI messaging into production modules.
• Developed Angular 20 admin panel features and AI/MCP-powered components inside the enterprise SaaS template.
• Served as business analyst on the YODER association platform alongside development: delivered presentations during client visits, analyzed business requirements with the client and translated them into development scope, and acted as the primary point of contact for the client.
• Took part in the client-facing project presentations at the close of the employee transportation and fleet optimization project.

YODER Association & Donation Operations Platform

• Business analysis: presentations during client visits, business requirements analyzed with the client and translated into development scope, and primary point of contact for the client
• Donor, family support, orphan sponsorship and campaign modules
• Income-expense tracking and staff operations modules
• Transaction sync and collection reconciliation via SOAP bank API
• Automated notifications via MutluCell SMS & WhatsApp/WATI
• 3CX API integration wiring call-centre workflows into the system
• Dynamic Excel reporting with ClosedXML
• Scheduled job automation with Hangfire and live alerts via SignalR

Tech: .NET 9 · ASP.NET Core · Angular 20 · PostgreSQL · Hangfire · SignalR · ClosedXML · SOAP/REST · MutluCell SMS · 3CX API · WhatsApp/WATI

AI-Powered Hotel Reservation Call Assistant

• Designed and shipped a multi-tenant application architecture
• Role-based access control (RBAC) and user management modules
• RAG knowledge base for contextual retrieval from enterprise content
• Low-latency voice assistant via STT → LLM → TTS pipeline
• Real-time voice streaming over WebSocket, SIP and WhatsApp channels; instant notifications in the management panel via SignalR
• AI call system automating multi-hotel operations

Tech: .NET Core · Angular 20 · PostgreSQL · CQRS / MediatR · Clean Architecture · SignalR · WebSocket · SIP · Hangfire · JWT · Serilog

Apartment Management System

• Ran sprint planning, task tracking and code review within a two-person software team
• CQRS read/write split → 40% improvement in query performance
• Modular, extensible architecture following SOLID principles
• Layered backend built for sustainability and scale
• MCP-based AI chatbot integrated with external services, producing contextual answers

Tech: .NET Core · Angular 20 · SQL Server · SignalR · Clean Architecture · CQRS · MediatR · EF Core · JWT

Enterprise Work Management Platform

• Ticket, task, project, purchase request and expense modules
• Drag-and-drop visual workflow editor built with @foblex/flow
• Scheduling and appointments via FullCalendar & Google Calendar
• Leave, remote-work, CV pool and asset assignment for HR
• Dynamic reporting and export with jsPDF and XLSX
• Ticket notes with mentions using the Quill rich-text editor
• Layered multi-tenant roles: super-admin, admin and user
• Real-time notifications and SLA reporting via SignalR

Tech: .NET Core · Angular 20 · SQL Server · SignalR · Clean Architecture · CQRS · MediatR · EF Core · JWT

Cloud-Based Document Management System

• Designed an end-to-end .NET Core + Angular full-stack architecture
• High-performance filtering and access layer for 10K+ documents
• Approve/reject flow for document requests, plus an approval-request mechanism that puts record changes behind sign-off
• Expiry review process scheduled with Hangfire: automatic email reminders with delay, disable and resolve steps
• Baskets for collecting documents and sharing them with other users
• MCP-based AI chatbot solution integrated with external services

Tech: .NET Core · Angular · MS SQL · CQRS · Hangfire

Multi-Tenant Employee Transportation & Fleet Optimization Platform

• End-to-end backend and admin panel covering tenant, company, department, stop, vehicle and rotation/expedition modules
• Automated route optimization engine using the VROOM solver on OSRM distance-matrix and route-geometry services, respecting vehicle capacity, shift time windows and maximum travel time/distance
• Bulk route preview, auto-generation and route consolidation workflows
• Real-time vehicle location, live expedition tracking and passenger-history sync via Arvento GPS/fleet integration
• Layered RBAC + Data-Scope authorization with granular role/user based entity and page permissions
• Real-time notifications and live tracking via SignalR; scheduled-job automation for passenger-history sync and auto route generation via Hangfire
• Took part in the client-facing project presentations at project close

Tech: .NET 9 · ASP.NET Core · Angular 20 · PostgreSQL · Clean Architecture · CQRS / MediatR · Hangfire · SignalR · VROOM · OSRM · Arvento GPS API

Bütçem — Offline Income, Expense & Budget Tracker

• Offline-first architecture on Flutter + Drift (SQLite); money kept as minor-unit integers, movements stored as double-entry postings
• Daily allowance: spendable balance minus the recurring payments still due this month, divided by the remaining days — category limits bind when tighter
• Bank statement (CSV) import with column mapping, duplicate detection, merchant→category guessing and one-tap undo
• Instalment purchases report spend in the purchase month and cash-out in their own month
• Recurring transactions, category budgets, savings goals, debt tracking, month-closing report and a home-screen widget
• Query discipline: per-screen query budget tests, a 10,000-record performance test, aggregates computed in single SQL statements
• 794 tests (pure services, database migrations, end-to-end screen flows); sideloaded signed APK with version.json based self-update

Tech: Flutter · Dart · Drift / SQLite · Riverpod · go_router · fl_chart · Kotlin (widget & installer channel) · Android

Harfsayı — Word & Number Game

• Server-authoritative flow: question generation, the clock and refereeing all live on the server, the client only draws — moving the device clock forward changes nothing
• Live duels, 2v2 team matches, spectator mode and a nightly 21:00 elimination tournament over SignalR
• An anagram index over a 62,326-word TDK dictionary feeds four features at once: best answer, garden level generation, bot answers and the uniqueness check for the final conundrum
• A Turkish morphology analyser splits words into root + suffixes; rejected words go to an appeal jury and accepted ones join the live dictionary
• Offline play: question pack embedded in the app, a drift/SQLite cache and idempotent sync keyed by device UUID — installable and playable in airplane mode
• Async duels, daily challenge, weekly leagues, seasons, word collection and a crossword generator (grid plus a clue filter over TDK definitions)
• 378 backend and 118 mobile tests plus end-to-end smoke tests covering WebSockets; deployed with Docker behind a permanent Cloudflare Tunnel address

Tech: Flutter · Dart · Riverpod · drift / SQLite · .NET 10 · ASP.NET Core · SignalR · PostgreSQL · EF Core · Docker · Cloudflare Tunnel · xUnit

Object-Oriented Programming Project

A modular C++ desktop stock-tracking app built on OOP principles.

E-Commerce Web Application

A dynamic cart and order management system built on a PostgreSQL backend.