Cal Henderson is the Co-founder and CTO of Slack. He has been working as a web applications developer for more than 15 years.

Slack was previously Tiny Speck, creators of the massively multiplayer online game Glitch. Prior to his work at Tiny Speck, Cal was Flickr’s Director of Engineering at Yahoo!. He was an inaugural member of the groundbreaking photo-sharing site, working alongside Flickr co-founder Stewart Butterfield, the now CEO and Co-Founder of Slack.

In 2006, Cal wrote the best-selling book Building Scalable Websites, and is currently working on a second edition. In his spare time he continues to publish articles on web application development and contribute to open source projects.