NIP-45
======

Event Counts
--------------

`draft` `optional` `author:staab`

Relays may support the `COUNT` verb, which provides a mechanism for obtaining event counts.

## Motivation

Some queries a client may want to execute against connected relays are prohibitively expensive, for example, in order to retrieve follower counts for a given pubkey, a client must query all kind-3 events referring to a given pubkey and count them. The result may be cached, either by a client or by a separate indexing server as an alternative, but both options erode the decentralization of the network by creating a second-layer protocol on top of Nostr.

## Filters and return values

This NIP defines a verb called `COUNT`, which accepts a subscription id and a filter as specified in [NIP 01](01.md).

Counts are returned using a `COUNT` response in the form `{count: <integer>}`. Relays may use probabilistic counts to reduce compute requirements.

Examples:

```
# Followers count
["COUNT", "", {kinds: [3], '#p': [<pubkey>]}]
["COUNT", "", {count: 238}]

# Count posts and reactions
["COUNT", "", {kinds: [1, 7], authors: [<pubkey>]}]
["COUNT", "", {count: 5}]
```