:ipv4: on Nostr: feld barrett at least the example of the project this spawned from used a simple in ...

feld (nprofile…xyvy) barrett (nprofile…25zh) at least the example of the project this spawned from used a simple in memory bloom filter to prevent double spend https://github.com/privacypass/challenge-bypass-server/blob/master/spendlist.go

although in some cases, you definitely want to allow a person to keep on replaying the same request as the rfc acknowledges
https://www.rfc-editor.org/rfc/rfc9577.html#name-replay-attacks