I’ll echo the other messages. It is not abuse to use ecto without persistence. I gave a talk a couple of years ago “Ecto Without a DB” that has an example of validating user input for search params. Here’s the video queued to that section.

Ecto has been purposefully split into ecto and ecto_sql. So it’s definitely not an “abuse” to use Ecto simply for handling and casting user-provided data when you’re not working with an SQL database.
You can use all the lovely features of Changesets including integration with Phoenix, even if you’re using your own persistence layer.

That would be my first attempt honestly. Once you have a changeset you can write your own logic for persistence. And schemas are useful anyway.

Or you could use a library like Xema. But for example you will still have to cast string-integers to integers, which means that you will have to validate those with custom validators or regexes.

I did not read the entire article you linked but to me validating before inserting makes no sense anyway. Just “validate” right after receiving the data (welll … the input) should be enough.