What database does Obsidian run on?

[Ooker]

why not a graph database?

Related question:

What does "link as first-class citizen" really mean?

The About page lists the philosophies of Obsidian: Local-first and plain text; Link as first-class citizen; Make it super extensible. At first I thought “Link as first-class citizen” simply means it will focus on links more than other software. But then I found out that First-class citizen has another meaning: In programming language design, a first-class citizen (also type, object, entity, or value) in a given programming language is an entity which supports all the operations generally av…