Check out around this area of the code to see how simple it is. All just files and directories: https://github.com/wting/hackernews/blob/master/news.arc#L16... .. the beauty of this simple approach is a lack of moving parts, and it's easy to slap Redis on top if you need caching or something.
There is a modern maintained variant at https://github.com/arclanguage/anarki/tree/master/apps/news as well if you want to spin up your own HN-a-like and have the patience.
File syncing between machines is pretty much an easily solved problem. I don't know how they do it, but it could be something like https://syncthing.net/ or even some scripting with `rsync`. Heck, a cronned `tar | gzip | scp` might even be enough for an app whose data isn't exactly mission critical.
Does anyone know of other open source applications with similar architectures like this?
There's a good reason everyone else just uses a relational database, and it isn't because everyone else is addicted to unnecessary complexity.
With filesystem as the storage you don't even need Redis, OS would cache the most recent files anyway.
You can get the software and language HN is based on here: http://arclanguage.org