Early job listings for “Application Engineer” required applicants to have “Fluency with the LAMP stack”. Linux, Apache, MySQL, PHP was and still is a popular choice for web applications which Slack started out as. Other requirements included an excellent understanding of networking, HTTP, JSON, and Smarty (template engine for PHP). According to an AWS case study “Tiny Speck—the original company name for what became Slack Technologies—used AWS in 2009 when it was the only viable offering for public cloud services.”