Full-time headcount: 3,500 | Headquarters: San Francisco | Year founded: 2013 | Most common skills: SQL, Data Analysis, Salesforce.com | Largest job functions: Sales, Engineering, Operations | What you should know: Having filed to go public in February, the on-demand food delivery service was already embarking on a big year. The pandemic introduced quarantines, and delivery demand skyrocketed. While DoorDash continues to clash with California regulators over whether its “dashers” must be classified as employees, its ambitions have only grown. It expanded its delivery service into pharmacy and grocery offerings. And after nearly doubling its employee base for the second time in two years, DoorDash has revamped its hiring process to focus on what it calls “engineering values” rather than culture fit.