It means 1 billion nodes though in an index.
Discussion
If I want to discover instances where Alice reacts to a kind 1 note authored by Bob, I’ll need indices for content in addition to indices for users.
Or suppose I want a chart of total zap amount in sats as a function of how far down a note is on a thread. Now suppose I only want to count zaps sent by frens (mutual follows) of the thread initiator. Or suppose I want a query even more complicated than that.
We’ll need indices for all content events, all zaps, all nostr events. Trillions.
You take all zap events and use some fast OLAP DB to crunch through this data instantly instead of wasting your time with a graph DB
This is a simple merge-join on 2 indexes that is cheap