thanks for the tip ! hoytech strfry is cool. I'll take a look

"The most original feature of strfry is a set reconcillation protocol based on negentropy. This is implemented over a nostr protocol extension that allows two parties to synchronise their sets of stored messages with minimal bandwidth overhead. Although primarily designed for relay-to-relay communication, this can also be used by clients.

Either the full set of messages in the DB can be synced, or the results of one or more nostr filter expressions. If the two parties to the sync share common subsets of identical events, then there will be significant bandwidth savings compared to downloading the full set."