I’ve been kicking around a project idea for years that would be a niche fit for these considerations. It’s effectively an extremely niche reference corpus of very field-specific data, effectively represented by JSON documents and having a few relationships that don’t require transactions. It wouldn’t be editable by clients at all. Every client would be nothing more than a consumer, and the database would be versioned and only edited by the maintainer.

That is certainly not a common use of web based APIs, to have an application that is read only every client, but the reason I came to this thread was because I’ve considered SQLite for this idea in the past.