&gt; A single global, mutable tree of untyped text is a bad persistence model.<p>In a strict sense, almost all software accessing standard hierarchical file systems is even just broken -- it breaks for certain concurrent operations, and there is no way to forbid them.<p>But still hierarchical filesystems are the best usable-by-default model I know. It&#x27;s a humane approach from a cognitive standpoint: the real world of &quot;things that exist only once, in one place&quot; is inherently hierarchical.<p>For different needs, it&#x27;s often easy enough to flatten data a bit and use tools like filename globs or regular expressions, to get a performant, good enough solution that is also maintainable.<p>For very specific needs, you can always use a relational, or whatever, DB.