• Slack gives teams something new, a home that connects their conversations, information, and software to create the context and shared understanding people need to come together. Slack is a layer of the business technology stack that brings together people, data, and applications – a  single place where people can effectively work together, find important information, and access hundreds  of thousands of critical applications and services to do their best work. The universal challenge for every organisation is to turn groups of individuals moving in many directions  into teams moving in the same direction.​ ​Slack gives teams something new, a home that connects their  conversations, information, and software to create the context and shared understanding people need to  come together. 
• The company, which went public through a direct listing in June, is now in more than 150 countries, is used by 65 of the Fortune 100 companies and has more than 10 million daily active users.
• Cal chat's about how he went from game developer to the co-founder of a multi-billion dollar company, his advice for aspiring entrepreneurs, and the future of work. Cal Henderson oversees the engineering organization at Slack. He is an experienced technology leader, having previously built and led the engineering team at Flickr, through its acquisition by Yahoo.
• As a popular speaker on engineering scalability, he authored the best-selling O’Reilly Media book Building Scalable Websites. He was a pioneer in the use of web APIs, and created the basis for OAuth and oEmbed, now used by YouTube, Twitter, and many others.

https://en.wikipedia.org/wiki/Web_API

• Cal has a BCS from the University of Central England, and was involved in London’s early online community through his work with the early digital community B3ta and his personal blog iamcal.com, which he has run for over 15 years. Cal now resides in San Francisco.