I think the reason they are so good at it is they are actually indexing and storing notes on their own server, not just searching relays and hoping they find them.

From the repo: Why "Antiprimal"? The name is tongue-in-cheek - we love Primal's infrastructure! But we want it to be accessible through anti-proprietary, standards-compliant interfaces. This gateway makes Primal's powerful features available to the entire Nostr ecosystem. Do you think the use of t...