I read here https://www.fediscovery.org/ :
> How is this related to relays?
>
> Relays can be used to get a more complete view of what is going on in the larger
> Fediverse. As such there are some similarities to this proposal.
>
> From an instance operator’s point of view the biggest difference is that using a relay
> comes with a higher cost. The instance needs to ingest and index everything the relay
> sends which takes up processing power and storage. A discovery provider will do that
> work for one or more instances.
>
> Implementation-wise we expect to see some similarities with how relays work, at least
> for real-time data. But discovery providers should be able to index historic data as
> well. So ingesting real-time data from instances is only part of the story.
> Querying instances for historic data is not currently something that relays do.