Gergely Sinka, Developer in Budapest, Hungary
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Gergely Sinka

Verified Expert  in Engineering

Software Developer

Budapest, Hungary
Toptal Member Since
June 3, 2020

Gergely is an innovative, full-stack developer. His early career was in manual and automated testing. Then he fell in love with coding and became a developer. He started by building and maintaining the back end of, an online meeting tool, and later turned to front-end development, which is his current focus. Gergely founded ConfigCat, a successful startup that he built from the ground up with a few friends.


Angular, .NET Core, TypeScript, Azure
Swift, Objective-C, Angular, React, JavaScript, .NET, Azure
Android, iOS, MacOS, .NET, Automated Testing




Preferred Environment

Redux, React, .NET Core, Angular

The most amazing...

...SaaS I created from the ground up is ConfigCat, a profitable, cross-platform feature flag service that's simple to learn and use.

Work Experience

Founder and Developer

2018 - PRESENT
  • Developed the .NET Core microservices-based back-end of ConfigCat from design to implementation.
  • Built the complete front-end application in Angular from design to implementation.
  • Created the complete CD/CD pipeline to support daily app development.
  • Wrote product-related articles, blog posts, and tutorials.
  • Managed social media channels and executed campaigns.
  • Provided and tracked continuous technical support to users.
Technologies: Angular, .NET Core, TypeScript, Azure

Software Developer

2015 - 2018
  • Developed parts of the back-end application for, a meeting tool that serves millions of users.
  • Fixed bugs and implemented endpoints and business logic to optimize client applications running on customers' computers.
  • Created a Chrome browser extension to integrate with Google Calendar.
  • Developed a front-end application allowing users to participate in online meetings.
  • Created front-end apps and websites using feature flags and A/B/n testing approaches.
Technologies: Swift, Objective-C, Angular, React, JavaScript, .NET, Azure

QA Engineer

2014 - 2015
  • Manually and programmatically tested, the online meeting tool, to ensure high quality.
  • Tracked issues and bugs in Jira related to every release and deployment.
  • Collaborated with the development team as a Scrum Master.
  • Introduced Agile and Scrum methodologies to the organization.
Technologies: Android, iOS, MacOS, .NET, Automated Testing

ConfigCat is a feature flag and remote configuration service that lets development teams decouple feature releases from code deployments. It provides a simple user interface, even for non-technical team members, to manage the features of their applications of any kind. The service supports A/B/n testing and canary releases by letting users turn on and off their applications' features easily, even from a mobile browser. ConfigCat minimizes the stress around deployments and ensures that each feature release is in sync with the marketing strategy and timeline.


React Redux, React, jQuery


Jira, Visual Studio, Xcode


JavaScript, HTML, CSS, C#, TypeScript, Objective-C, Swift


Agile, REST, DevOps, Automated Testing


ASP.NET, Angular, .NET Core, .NET, Angular Material, Razor Pages, Redux


Visual Studio Code (VS Code), Azure PaaS, Linode, Azure, MacOS, iOS, Android




Writing & Editing

Collaboration That Works

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