Network file systems are <i>hard</i>. There are 30+ years of posts in various places of the Internet, hundreds of books, and dozens of implementations&#x27; source listings that you can read.<p>Dropbox have exceptional engineering talent, and a mature code base. Nobody else before or since, has ever come even close to what they have, quality- or feature-wise.<p>That they make it look easy doesn&#x27;t mean that it <i>is</i> easy. It&#x27;s like saying, all this guy ever does is hitting the puck in the net skating backwards, I don&#x27;t understand why nobody else is able to do it?