[aryastark]

I was under the impression Dropbox is a UI to Amazon S3. I use them and don't mean to deny it's a slick package. But I could duplicate the entire thing in about a day with inotify and rsync. The scaling is mostly on Amazon.

That said, I must point out that the scaling issues all of these super modern "change the world" companies, such as Twitter and Facebook, have are purely for the purpose of centralizing power. It's a self-inflicted headache. It's great business to be in control of millions of users. But it's a sad state of affairs for the internet in general. We've gone from open, decentralized, and peer-to-peer protocols to one company controlling everything.

There are interesting scaling problems. But Facebook isn't one of them.

[staunch]

> But I could duplicate the entire thing in about a day with inotify and rsync. The scaling is mostly on Amazon.

No, you could duplicate a narrow piece of Dropbox's functionality in a day. You could not even get anywhere near duplicating the product and the service in anything less than months.

[aryastark]

Dropbox pretty much uses librsync and, I believe, inotify on Linux. With Amazon S3. That is Dropbox. Literally.

Polishing any product takes time. But that's universal and has nothing to do with engineering. What exactly is non-trivial about Dropbox?

[brianchu]

Some of the technical challenges I can think of:

1. Version control.

2. LAN sync.

3. Dropbox probably also does a lot to try and minimize their S3 costs - so probably a good deal of compression/duplication-detection on the backend.

4. Any and all networking issues. Even if using OSS gets you 98% of the way, Dropbox probably gets you 100% of the way.

5. Performance. I don't know what Dropbox is doing, but about a year ago I tested out Google Drive, SkyDrive, Dropbox, and SugarSync. I didn't want to use Dropbox because it gives you the least free storage, but Dropbox was consistently 2x faster than the competition (without using LAN sync). That makes a huge difference so I switched to it, and if Dropbox engineers are beating out Google and Microsoft engineers, they're clearly doing something special.

[EnderMB]

It's a shame that the "Shit HN Says" Twitter account is dead. This would be a dead cert to end up on there.

In all seriousness, from a highly abstracted view, Dropbox isn't all that complicated. However, the same things are said about numerous other projects. I remember when Stack Overflow took off, and everyone around here said "I could build Stack Overflow in a weekend".

It turns out that, yes, you can build Stack Overflow in a weekend. However, all you've managed to build is a basic Q&A site. What you've missed is practically everything that makes Stack Overflow work. The rep count probably doesn't work as well, the moderator controls aren't there, the OpenID integration isn't there, the markdown controls aren't as sophisticated, it's slower, etc.

I don't have a link to it, but not long ago there was a repost of the original "Show HN" for Dropbox, where there were similar criticisms of how "trivial" Dropbox is to implement. The devil is in the details.