Kind of. There are specs and there are blog posts and there are also existing implementations to review - but there isn’t a one size fits all solution, its more of a concept. NIP-65:

GitHub

nips/65.md at master · nostr-protocol/nips

Nostr Implementation Possibilities. Contribute to nostr-protocol/nips development by creating an account on GitHub.

Mike Dillger’s post:

mikedilger.com

Hodlbod’s post:

hodlbod (npub1jl…jynqn) on Nostr

Long-form Content: nostr (What is the Outbox Model?) by hodlbod

What is the Outbox Model? -- seen on nos.lol, relay.nostr.band, christpill.nostr1.com, nproxy.kristapsk.lv, nostr.bitcoiner.social, a.nos.lol, henh...