This might not be the answer you are looking for – but I’d reach for sqlite3. It also can be up to 35% faster than raw file access.
Trouble is, current state of the art of sqlite3 in Elixir does not support Ecto 3 (latest version of the de facto DB persistence library); only version 2 which is now quite old. I am working on bringing Ecto 3 to sqlite3 but it definitely is not going to be ready tomorrow.
Using sqlite3 will rid you of the potential file overwriting problem as well since there the ID is… you know, the database ID, not the filename itself. What’s more, an embedded DB like sqlite3 gives you the ability to sort and filter out of the box.
If that doesn’t sound tempting to you then I’d be happy to help you exactly with the File / IO API. However, you should have in mind that functions like stat can have differing behaviours between different OS-es. Which is all the more reason to opt for a database.
Any particular scenario you would like help with?
If you would like something that basically manages uploads to your app then Waffle might be exactly what you are looking for (it can put all stored files into Amazon’s S3 or in your local filesystem).
