ngit-grasp/docs/reference/relay-limits.md

nostr-relay-builder Limits

This document describes the rate limiting, throttling, and query limits in nostr-relay-builder version 0.44. These are the limits that apply to ngit-grasp and any relay built with this crate.

Note: Other relay implementations (strfry, nostream, etc.) have different limits. This document focuses on nostr-relay-builder specifically.

Hard Limits (Cannot Be Changed)

These limits are enforced and cannot be overridden by configuration:

WebSocket Message Limits (from tungstenite)

Limit	Default Value	Source
max_message_size	64 MB (67,108,864 bytes)	tungstenite default
max_frame_size	16 MB (16,777,216 bytes)	tungstenite default

nostr-relay-builder does not override these tungstenite defaults.

Practical impact: A single REQ message or EVENT with extremely large content could hit these limits. A filter with ~1,000,000 32-byte event IDs (~32MB in JSON) would fit, but 2 million would not.

Negentropy Frame Limit

Limit	Value	Source
frame_size_limit	60,000 bytes (60KB)	Hardcoded in inner.rs

let mut negentropy = Negentropy::owned(storage, 60_000)?;

If reconciliation needs more data, negentropy splits across multiple NEG-MSG round-trips automatically.

No Hard Limits On

nostr-relay-builder does NOT enforce hard limits on:

Item	Hard Limit?	Notes
Tag values per filter (#e, #p, etc.)	❌ None	Only limited by message size
Filters per REQ array	❌ None	Only limited by message size
Filter JSON size	❌ None	Only limited by WebSocket message
Authors per filter	❌ None	Only limited by message size
Kinds per filter	❌ None	Only limited by message size
IDs per filter	❌ None	Only limited by message size

Configurable Limits (Server-Side)

These limits have defaults but can be configured via RelayBuilder:

Query/Response Limits

Setting	Default	Builder Method
default_filter_limit	500	.default_filter_limit(n)
max_filter_limit	None (no cap)	.max_filter_limit(n)

Behavior:

1. If filter has no limit field → server applies default_filter_limit (500)
2. If filter has limit > max_filter_limit → clamped to max_filter_limit
3. If filter has specific ids → uses ids.len() as limit

Rate Limiting

Setting	Default	Description
max_reqs	500	Max active subscriptions per session
notes_per_minute	60	Token bucket rate for EVENT writes

Rate limiting uses a token bucket: tokens regenerate proportionally over time, each EVENT consumes 1 token.

Connection/Session Limits

Setting	Default	Description
max_connections	None	Max concurrent WebSocket connections
max_subid_length	250	Max characters in subscription ID

REQ vs Negentropy Limits

Aspect	REQ (NIP-01)	Negentropy (NIP-77)
Events returned	Limited (default: 500)	Unlimited (all IDs returned)
Filter limit applies?	✅ Yes	❌ No
Returns full events?	✅ Yes	❌ No (only EventId + Timestamp)
Message size limit	64MB (WebSocket)	60KB per frame

Why negentropy returns all: It only returns ~40 bytes per event (ID + timestamp) for set reconciliation. Full events are fetched separately after identifying what's missing.

Quick Reference

Limit	Value	Type
WebSocket message	64 MB	Hard (tungstenite)
WebSocket frame	16 MB	Hard (tungstenite)
Negentropy frame	60 KB	Hard (hardcoded)
Tags per filter	None	Soft (message size only)
Filters per REQ	None	Soft (message size only)
Events per REQ	500	Configurable default
Max subscriptions	500	Configurable default
Write rate	60/min	Configurable default

ngit-grasp Configuration

ngit-grasp uses defaults (no custom limits configured):

let builder = RelayBuilder::default()
    .database(database.clone())
    .write_policy(write_policy.clone());

Additionally, ngit-grasp's memory database limits to 100,000 events (LMDB has no such limit).

Related

• NIP-01: Basic Protocol
• NIP-77: Negentropy Sync
• nostr-relay-builder docs
• tungstenite WebSocket limits