T-SQL Developer in Guangzhou, Guangdong, China
Consultant, Developer2005 - PRESENTFreelance
- Built a ticket management system for events.
- Created numerous company and product websites and applications.
- Joined existing teams to temporarily boost productivity.
- Designed and implemented a CRM with automation capabilities.
- Acted as an external auditor reviewing quality, robustness, and security.
Developer2016 - 2018ZampleBox
Technologies: ASP.NET Core, AngularJS, SQLServer, Azure
- Worked as a core developer on the main eCommerce product.
- Helped drive the development of new core business features.
- Migrated the application from ASP.NET MVC 5 to ASP.NET Core.
Tech Lead2015 - 2017WeTrada
Technologies: .NET, Azure
- Set up a brand new unique online shopping portal.
- Automated a shopping experience that offers customized communication flows.
Founding CTO2013 - 2016Postvid, Ltd.
Technologies: C#, DurandalJS, Azure
- Built a highly scalable back-end service for uploading, handling, converting, and composing user media (photos, videos, and audio).
- Created a web application for creating a fully customized video greeting card.
- Created a full-stack order pipeline service for order and payment tracking with full QOS reporting and alerting.
- Established the technical vision and led all aspects of IT-related development.
- Conducted research and case studies on cutting-edge technologies.
API Developer2015 - 2015Litmus (via Toptal)
Technologies: .NET, AWS
- Created a high performance API with synchronization capabilities for external services.
.NET Developer2015 - 2015hopIN (via Toptal)
Technologies: .NET, Azure
- Migrated over an existing software solution to a more efficient hosting plan on Azure.
- Solved a number of issues with the application.
PHP Developer2015 - 2015Bumptext (via Toptal)
Technologies: PHP, XAMPP
- Solved numerous issues with the existing software solution.
- Proposed a path forward.
Azure Expert2015 - 2015Silec (via Toptal)
Technologies: Azure, .NET
- Helped to create a deployment strategy for hosting the in-house web application on Azure.
Consultant, Developer2011 - 2015Web Power
- Served as product owner and architect for a major new email marketing product.
- Developed and implemented various web applications and integration solutions for numerous clients.
- Worked as lead architect on an experimental new back-end system for handling all data transactions for the entire product family.
- Consulted both internally and externally on various IT-related topics.
- Handled developer training for clean and testable code with state of the art technologies and practices.
Lead Developer2006 - 2011Infocaster
- Created services for mass news profiling and analytics.
- Built a recommendation system matching users based on online behavior, suggesting contacts and sources.
- Created online web portals for displaying and managing news (similar to Google Now).
- Created desktop applications for numerous clients, combining features such as RSS tracking, weather information, and commenting.
- Built various in-house websites and applications for top 500 enterprises.
- Postvid Consumer Platform (Development)
Postvids are a new breed of direct marketing and impact marketing communication tools. Postvids drive home your brand and campaign messages through hi-definition LCD screens and powerful audio speakers encased in a full color, fully customizable, printed brochure or booklet.
- WeTrada Website (Development)
You get together with others who want to buy the same product. You buy the things you love together as a group! Now it’s possible to place orders directly with the manufacturer without having to deal with cost-adding merchants and middle men. Straight from the factory to your home. The savings are spectacular!
- Koen is a mentor in the Toptal Global Mentor’s Program. This program is a partnership between Toptal and General Assembly to provide high quality mentorship for students from minority and low income backgrounds who are looking to begin their careers as professional software engineers. Koen shows commitment to diversity in tech by mentoring a General Assembly student every week for a year, covering everything from coding tips and tricks to advice on making it in the industry.
FrameworksASP.NET Core, ASP.NET Core 2, Aurelia, .NET, ASP.NET, Durandal, ASP.NET Web API, ASP.NET MVC, Bootstrap, Angular, AngularJS, Windows Presentation Foundation (WPF), Windows Communication Framework (WCF), PhoneGap, Cordova, Knockout.js
PlatformsAzure, Azure Functions
Libraries/APIsjQuery UI, jQuery, SignalR, Node.js, Twitter API, LinkedIn API, Facebook API
ToolsMicrosoft Visual Studio, Git, Subversion (SVN), Mercurial
StorageAzure Cosmos DB, MySQL, Microsoft SQL Server
OtherScalable Architecture, Big Data
ParadigmsFunctional Programming, Reactive Programming, Concurrent Programming
- Bachelor's degree in Computer Science2005 - 2008Windesheim University - Netherlands