As I think I said elsewhere, we allowed people to use a database if they wanted to (and could install it themselves on the dev VM we gave them), but then we would include looking at how they designed the schema, how much thought did they put into connection handling, etc.

But most of the people who successfully passed this didn't use a database, it just wasn't enough data to be meaningful - thousands of rows at most.

Yeah, or you could use the opportunity to demonstrate that you know how to roll your own data structures, provided you've clarified that the dataset isn't likely to grow. Instead of showing them you know how to install a database.