I mean you can use sqlite as an index and then rebuild all of Lucene on top of it. It's non-trivial to build search quality on top of actual search libraries too.

O'Reilly's "Relevant Search" isn't the worst here, but you'll be porting/writing a bit yourself.

> Does anyone know good resources for this to learn and draw inspiration from?

Is there a reason why something more custom built, like ParadeDB Community edition won't meet your needs?

I understand you're speaking about SQLite, while ParadeDB is PostgreSQL but as you know, it's non-trivial to get good search quality, so I'm trying to understand your situation and needs.