The taxonomy and metadata, as you put it, is defined by the moderators/community of each database. We just give them drag-and-drop tools to do so :)

ah i meant to ask how it was designed in the backend

I won't get too deep into our architecture, but needless to say letting users dynamically edit/add/remove fields in their databases is not easy. We use Postgres + Prisma as our ORM, and I'm fairly happy with its DX re: handling this level of complexity

I would put everything in JSON(b) column since you're using Postgres anyway....