Proof of work.
Payment of 21 sats using NFC card on Android with #nostr #safebox on left.
Updated balance and transaction are shown in Nostr Wallet Connect in #damus iOS client on right.
Instantaneous.
https://video.nostr.build/8cae0012419058a3739579f3f0eb38ddbc7b94f229a9379bf512104fc006f9a4.mp4