Sefa Şıhlar profile picture: Anonymous mask with the words 'Veni, vidi, vici'

Veni, vidi, vici

Sefa Şıhlar

Full Stack .NET Developer & Project Manager, security-minded

I build scalable, secure enterprise systems with .NET Core, microservices and React. Right now I lead the development of a global fuel management system used in 35 countries and at more than 27,000 stations.

See my projects My GitHub (opens in a new tab)
  • C#
  • .NET Core
  • ASP.NET
  • React
  • JavaScript
  • HTML5
  • CSS3
  • Bootstrap
  • Sass
  • Python
  • Django
  • Selenium
  • MSSQL
  • PostgreSQL
  • MongoDB
  • MySQL
  • Redis
  • SQLite
  • RabbitMQ
  • Docker
  • Git
  • GitHub
  • Azure
  • AWS
  • Linux
  • Nginx
  • Swagger
  • Postman

Drag to rotate

sefa@sihlar: ~
sefa@sihlar:~$ whoami
Sefa Şıhlar
Full Stack .NET Developer & Project Manager, security-minded
sefa@sihlar:~$ cat stack.json
{
  "backend": [".NET Core", "ASP.NET", "Web API", "RabbitMQ"],
  "frontend": ["React"],
  "data": ["MSSQL", "PostgreSQL", "MongoDB", "Redis"],
  "ops": ["Docker", "Git", "CI/CD"]
}
sefa@sihlar:~$ ./security --status
[ ok ] VPN tunnels between distributed systems
[ ok ] OAuth2 + JWT authentication with IdentityServer
[ ok ] Security tests: SQLi, XSS, DDoS
sefa@sihlar:~$ uptime
35 countries, 27,000+ stations (fuel management system)
type help and press Enter

The developer behind the mask

The short version is on the card. What I work on, how I work, where I studied and the languages I speak are in the README.

sefasihlarREADME.md

Hi, I'm Sefa

I'm a Management Information Systems graduate of Akdeniz University. I build enterprise software and multi-tier applications, and my work centers on systems that scale and stay secure.

What I'm doing now

Since March 2024 I've been working in İstanbul as a Full Stack Developer and Project Manager, leading the development of a global fuel management system used in 35 countries and 27,000 stations.

I design the APIs with .NET Core, build frontend modules with React, run deployments with Docker and CI/CD, and set up VPN-based secure channels between distributed systems.

How I work

  • Clean Code, SOLID principles and design patterns
  • Code reviews and the GitFlow branching model
  • Sprint planning, backlog management, Scrum and Agile
  • Making technical decisions together with the team
  • Finish learning. This box stays empty.

Education

SchoolAkdeniz University
FacultyApplied Sciences
DepartmentManagement Information Systems
Years2019–2023, Antalya

Languages

  • Turkish Native
  • English B1
    1. A1
    2. A2
    3. B1 (my level)
    4. B2
    5. C1
    6. C2
    A1, A2 and B1 certificates from BTK Akademi
Sefa Şıhlar profile picture: Anonymous mask with the words 'Veni, vidi, vici'
Access
root
Location
İstanbul, Türkiye

Sefa Şıhlar

Full Stack .NET Developer & Project Manager

Veni, vidi, vici
On GitHub
since 2019
Public repositories
21+ public repositories

My career, commit by commit

Newest commit on top. I started as a backend developer in 2023; today I combine full stack development with project management. My university years are here too, as a branch merged into main.

  1. Fullstack Developer & Project Manager

    – present

    Global fuel management system

    Current

    Istanbul, Türkiye

    • Lead the development of a global fuel management system used at 27,000 stations in 35 countries.
    • Build secure, VPN-based communication channels between distributed systems.
    • Design and implement APIs with .NET Core Web API, microservices and REST/SOAP.
    • Deliver React frontend modules that integrate with the backend services.
    • Manage containerized deployments with Docker and CI/CD pipelines.
    • Maintain and optimize a multi-database environment: MSSQL, PostgreSQL, MongoDB and MySQL.
    • Coordinate project planning, sprint management and technical decision-making.
    • Set up monitoring and logging processes that reduce downtime and improve system reliability.
    • .NET Core
    • Web API
    • Microservices
    • REST/SOAP
    • VPN
    • React
    • Docker
    • CI/CD
    • MSSQL
    • PostgreSQL
    • MongoDB
    • MySQL

  2. Backend Developer

    –

    Meta Akdeniz

    Antalya, Türkiye

    • Developed web applications with ASP.NET Core and MVC.
    • Implemented authentication and authorization with IdentityServer.
    • Contributed to modular e-commerce and management systems built on microservices.
    • Built automation solutions with Python, Django and Selenium.
    • ASP.NET Core
    • MVC
    • IdentityServer
    • Microservices
    • Python
    • Django
    • Selenium

  3. Management Information Systems

    –

    Akdeniz University, Faculty of Applied Sciences

    Graduated

    Antalya, Türkiye

The tools I reach for

Most of my work is in C# and .NET. I use React for interfaces, relational and NoSQL databases for data, and Docker with CI/CD to ship.

Backend and APIs

I write APIs for enterprise systems and high-traffic integrations, and keep data access fast with EF Core and Dapper.

  • C#
  • .NET Core
  • ASP.NET MVC
  • Web API
  • .NET Framework
  • Entity Framework Core
  • Dapper
  • SignalR
  • REST
  • SOAP

Architecture

I split growing systems into independent services and connect them through events on RabbitMQ.

  • Microservices
  • Event-driven architecture
  • RabbitMQ
  • Ocelot API Gateway
  • DDD
  • N-layer architecture
  • Clean Code
  • SOLID
  • Design patterns

Identity and security

I set up authentication with OAuth2 and JWT and connect distributed systems to each other over VPN. More in the security section.

  • IdentityServer4
  • OAuth2
  • JWT
  • ASP.NET Core Identity
  • VPN integration
  • Security testing

Databases

I write stored procedures and triggers, tune MSSQL performance, and run environments where several databases work side by side.

  • MSSQL
  • PostgreSQL
  • MongoDB
  • MySQL
  • Redis
  • SQLite

Frontend

I build React modules wired to backend services, and responsive interfaces that work just as well on a phone.

  • React
  • JavaScript (ES6+)
  • Ajax
  • HTML5
  • CSS3
  • Bootstrap
  • Sass

DevOps and cloud

I package apps with Docker and ship them to staging and production through CI/CD pipelines.

  • Docker
  • CI/CD
  • Git
  • GitHub
  • GitFlow
  • Azure (basics)
  • AWS (basics)
  • Linux
  • Nginx

Automation and testing

I write web and desktop apps in Python, browser automation with Selenium, and API, integration and load tests.

  • Python
  • Django
  • Tkinter
  • Selenium
  • API and integration tests
  • Load testing

Monitoring and process

I set up monitoring and logging to reduce downtime, and coordinate sprint planning, the backlog and technical decisions.

  • Serilog
  • Monitoring and logging
  • Scrum
  • Sprint planning
  • Backlog management
  • Code review

I design security in from the start

Encrypted channels, token-based authentication, validated input and monitoring aren't patches I add after launch. They're the first decisions in the architecture.

5/5 applied

My secure-by-design checklist

# Not live data from any system: the checks I go through when I design one.

  • Encrypted transport

    TLS to the client, a VPN tunnel between systems.

  • Token-based identity

    With OAuth2 and JWT, every request proves who sent it.

  • Input validation

    Parameterized queries and output encoding against SQL injection and XSS.

  • Rate limiting

    Limits for traffic spikes and a DDoS plan written before it's needed.

  • Logging and monitoring

    Central logs and alerts, so problems surface before users notice.

What I've done in the field

The work behind the checklist: what I've built, tested and been certified in.

  • VPN-secured integration

    I built VPN-based secure channels between the distributed parts of a global fuel management system used in 35 countries and at 27,000+ stations.

  • Authentication and authorization

    I set up token-based authentication with IdentityServer4, OAuth2 and JWT: Google sign-in on FreeCourse, ASP.NET Core Identity on KitX.

  • Security testing

    I run security tests against SQL injection, XSS and DDoS scenarios, and load tests to see how a system behaves under heavy traffic.

  • Monitoring and logging

    I set up monitoring and logging processes that reduce downtime. In my projects I use Serilog for structured logs.

  • Incident detection and response

    I hold a BTK Akademi certificate in spotting security incidents early and responding to them with a plan.

    View certificate

  • DoS/DDoS protection

    I hold a BTK Akademi certificate in how denial-of-service attacks work and how to protect systems against them.

    View certificate

Certificates

All four are from BTK Akademi, the training platform of Türkiye's ICT Authority, and two are about cyber security. Flip a card to see what it covers.

  • Cyber security

    Cyber Incident Detection & Response

    BTK Akademi

    Cyber Incident Detection & Response

    Covers
    Recognizing the signs of a security incident early and responding to it with a clear plan.
    Issued by
    BTK Akademi
  • Cyber security

    DoS / DDoS Attacks and Protection

    BTK Akademi

    DoS / DDoS Attacks and Protection

    Covers
    How denial-of-service attacks work and how to keep systems protected against them.
    Issued by
    BTK Akademi
  • DevOps and version control

    Git & GitHub: Version Control Systems

    BTK Akademi

    Git & GitHub: Version Control Systems

    Covers
    Version control with Git and working as a team on GitHub.
    Issued by
    BTK Akademi
  • Language

    English

    BTK Akademi

    • A1
    • A2
    • B1

    English A1, A2, B1

    Covers
    English at three levels, from A1 to B1. B1 is the first independent-user level of the CEFR.
    Issued by
    BTK Akademi

Systems I've built

Some of it runs in the field across 35 countries, some of it is open source on GitHub. I can't share code from closed-source work, but I can show what I built and how it turned out.

Global fuel management system

  • Enterprise, closed source
  • My role: Fullstack Developer & Project Manager
  • Since March 2024

I lead development of a fuel management system used at stations around the world. Project planning, sprint management and technical decisions are my responsibility too.

  • 35 countries where it runs
  • 27,000+ stations running it
  • Built VPN-based secure communication channels between distributed systems.
  • Designed and built REST and SOAP APIs with .NET Core Web API and microservices.
  • Manage containerized deployments with Docker and CI/CD pipelines.
  • Set up monitoring and logging that cut downtime and made the system more reliable.
  • .NET Core Web API
  • Microservices
  • REST
  • SOAP
  • React
  • Docker
  • CI/CD
  • MSSQL
  • PostgreSQL
  • MongoDB
  • MySQL

Illustrative visualization

FreeCourse microservices platform

  • Open source
  • Online course platform

A microservice architecture I built for an online course platform. Each service owns its database; requests from the client reach the services through the Ocelot API gateway, and IdentityServer4 handles authentication.

  • The Ocelot API gateway routes requests to the services from a single entry point.
  • JWT-based authentication with IdentityServer4, including Google sign-in.
  • A database per service: MongoDB for Catalog, Redis for Basket, PostgreSQL with Dapper for Discount.
  • DDD layers in the Order service (Domain, Application, Infrastructure) on EF Core and SQL Server.
  • ASP.NET Core MVC
  • Ocelot
  • IdentityServer4
  • JWT
  • EF Core
  • Dapper
  • AutoMapper
  • Swagger

View the code on GitHub (opens in a new tab)

Client

  • Web UI, ASP.NET Core MVC

Gateway

  • Ocelot, API Gateway
  • IdentityServer4, JWT

Services

  • Catalog
  • Basket
  • Discount
  • Order
  • PhotoStock
  • FakePayment

Data

  • MongoDB
  • Redis
  • PostgreSQL, Dapper
  • SQL Server, EF Core
FreeCourse architecture: four layers from client to data

Open-source repositories

A selection of my projects with public code.

  • KitXReal-time REST API

    An ASP.NET Core REST API with a web UI in an N-layer architecture (API, Core, Repository, Service), using Identity and JWT for authentication and SignalR for real-time clients.

    • ASP.NET Core
    • SignalR
    • EF Core
    • SQL Server
    • Serilog
    GitHub

  • OnlineAcademyOnline academy

    An N-layer ASP.NET Core MVC 6 and REST API project with separate academy, administrator, teacher and student apps and a caching layer.

    • ASP.NET Core MVC 6
    • REST API
    • N-layer architecture
    GitHub

  • Academy-1.0.1Meta Akdeniz Academy

    An academy platform built in BusinessLayer, DataAccess, EntityLayer, WebApi and WebUI layers, developed from version 1.0.0 to 1.0.1.

    • Web API
    • N-layer architecture
    GitHub

  • NewStudentManagmentStudent management system

    A student management app built on ASP.NET Core MVC 6 and a REST API, in an N-layer architecture with a caching layer.

    • ASP.NET Core MVC 6
    • REST API
    • N-layer architecture
    GitHub

  • ShopAppE-commerce application

    An e-commerce application I built with ASP.NET Core 6; its second version lives in the ShopApp-2 repository.

    • ASP.NET Core 6
    • C#
    GitHub

  • language:pythonPython automation tools

    Selenium bots for Instagram follows and messages, a Tkinter desktop app for decision-making techniques, and LeetCode and HackerRank algorithm solutions.

    • Python
    • Selenium
    • Tkinter
    GitHub

This is a selection; I have 21+ public repositories on GitHub. All repositories, live, below My GitHub profile (opens in a new tab)

My code, in the open

This section reads live from the GitHub API: my public repositories, the languages they use and when they last changed. If the API can't be reached, you see the last saved snapshot.

Offline snapshot, 16 October 2026

Sefa Şıhlar

@sefasihlar

Web Developer

On GitHub since 2019

Public repositories
21
Followers
6
Total stars
2
Most-used programming language
C#

Languages by repository count

  • HTML 35%
  • C# 25%
  • Python 25%
  • JavaScript 10%
  • Other 5%

Each repository counts once, under the main language GitHub detects. In ASP.NET MVC projects, Razor views (.cshtml) and front-end assets can make a C# project show up as HTML or JavaScript.

Repositories

See all repositories on GitHub (opens in a new tab)

Contribution graph

My GitHub contributions over the last 12 months; each square is one day.

Frequently asked questions

Short answers about who I am, what I work on and how to reach me.

If your question isn’t here, ask me directly.

Who is Sefa Şıhlar?

Sefa Şıhlar is a Full Stack .NET developer and project manager based in Istanbul, Türkiye, and a graduate of Akdeniz University (Management Information Systems). Sefa works on ASP.NET Core, microservice architectures, React and secure system integration, and leads the development of a global fuel management system used in 35 countries and 27,000 stations.

What technologies does Sefa Şıhlar work with?

C#, .NET Core, ASP.NET MVC and Web API, Entity Framework, Dapper, RabbitMQ, IdentityServer, OAuth2 and JWT, React, MSSQL, PostgreSQL, MongoDB, MySQL, Redis, Docker, Git, and Python (Django, Selenium, Tkinter).

What cybersecurity experience does Sefa Şıhlar have?

Sefa has built VPN-based secure communication channels between distributed systems, carried out security testing against SQL injection, XSS and DDoS scenarios, and builds authentication and authorization with IdentityServer, OAuth2 and JWT. Certifications include Cyber Incident Detection & Response and DoS/DDoS Attacks and Protection.

What projects has Sefa Şıhlar worked on?

A global fuel management system used in 35 countries and 27,000 stations, the FreeCourse microservices platform built on Ocelot and IdentityServer4, the SignalR-powered KitX REST API, the OnlineAcademy and Meta Akdeniz Academy learning platforms, plus several e-commerce and automation projects.

How can I contact Sefa Şıhlar?

Send an email to sihlarsefa7@gmail.com, or reach out via LinkedIn (linkedin.com/in/sefasihlar) or GitHub (github.com/sefasihlar).

If you have an idea,
let’s build it together.

I’m open to new projects, collaborations and technical conversations. If you want to talk about a backend, a microservice architecture or a secure integration, email is the most direct way to reach me.

sihlarsefa7@gmail.com

The terminal at the top of the page accepts commands too; type help to start.

Istanbul, Türkiye