According to the Twitter Careers page: Software Engineering, Design &amp; UX Research, Sales &amp; Revenue, Product Management, Infrastructure Operations, Media &amp; BizDev, Trust &amp; Safety, User Services, Legal, Finance, Workplace &amp; Admin, Marketing &amp; Communications, HR &amp; Recruiting.<p>As far as engineering, take a look: <a href="https:&#x2F;&#x2F;about.twitter.com&#x2F;careers&#x2F;teams&#x2F;software-engineering" rel="nofollow">https:&#x2F;&#x2F;about.twitter.com&#x2F;careers&#x2F;teams&#x2F;software-engineering</a><p>Many companies are much more complex than you might imagine from the outside. Also, a lot of it is meta-headcount: managers, facilities, food service, payroll, benefits, recruiters, lawyers, HR people, etc. all scale at least partially with headcount.<p>You&#x27;ll notice many of the jobs are with companies Twitter has acquired or various platform-level projects, like Fabric, Vine, TellApart, Finagle, etc.