I think it depends on what ones actions performed will be. If I am rendering a blog from some markup files, I might not need to build my own persistence or thin

I think it depends on what ones actions performed will be. If I am rendering a blog from some markup files, I might not need to build my own persistence or things like that. The information flow is unidirectional. In such and other simple cases, a relational database is overkill. It is also not too difficult to switch from plain text files to a database, if one does this step in time, before implementing ones own persistence, joins and whatever on basis of files.