Ask HN: Is it possible to have forum type community running without a database?

As for the file format, it would be best to stick with standard formats like JSON, XML, or YML. Or the standard serialization method for your favorite language, such as pickle() for Python and serialize() for PHP. Try not to invent a brand-new format, it's going to be error-prone and generally slower than using a standard format.

A more difficult task is to maintain an index of some sort, separate from all the individual files, so that you won't have to read and parse every single file in order to generate the forum listing. Whenever a reply is posted, you'll need to bump a thread to the top of the listing. Think about how you can implement this without modifying or renaming several files at a time.

And then you'll need to ask yourself how you're going to prevent inconsistencies in your data over the next few years. What if you decide to add a new field to the JSON schema and all the old files don't have that field? What if you delete a thread but an error occurs halfway through and some of the individual posts still remain? You'll need to write logic to handle such edge cases as well.

SQLite solves a lot of these problems while offering the same sort of performance, if not better, on resource-constrained environments. As far as SQLite is concerned, a Raspberry Pi is a very powerful machine. There's no reason why you sholdn't be able to enjoy all the benefits of flat files together with all the benefits of a relational database.

I have done almost exactly what you're talking about with a raspberry pi, using Ruby on Rails (3.0.x era) and sqlite. the Rasppi (model B) had enough horsepower to run in development mode on webrick and handle ~5 rps with page rendering and database calls, and that was in develop! when running in production, rails does less reloading of resources, so should be even more efficient.

This line is the key to the question. Simply roll back time until the specs of the Pi would be a "decent" or at least "cheap" webserver for that time, the kind of server you'd run a small forum upon at that time. OR if not decent for bare metal hardware, decent for a virtualized image on a bigger server.

Its not like 2014 is the first year in human history with webservers or web based forums.

So people were running forums on tiny virtualized servers with about those specs on linode perhaps just a couple years ago. Perhaps even today either on very tiny linodes or competitors.

The only real problem is the software. So use old stuff open to individual and class of vulnerabilities that were fixed 5 years ago, or take an obese beast of a modern forum and give it a liposuction?

Look into puppet and run the master somewhere else and automate it enough that you can go from a bare metal Pi to a live host in ten minutes or so. You'll be doing it again sooner or later at a time not of your choosing, so may as well get it right now.

Also, implement a backup strategy and automate its restoral process (and integrate with above)