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Nostr Relays

Relays are the servers that store and forward Nostr events. For financial applications, relay selection and reliability are critical considerations.

What Are Relays?​

Relays are:

  • Message brokers that accept and serve events
  • Decentralized - anyone can run one
  • Independent - each has its own policies
  • The backbone of Nostr's infrastructure

Relay Types​

Free Relays​

Open to everyone:

  • No cost to write/read
  • Often run by enthusiasts
  • May have limited retention
  • Higher spam potential

Require payment:

  • One-time or subscription fee
  • Better spam filtering
  • Higher reliability
  • Longer data retention

Private Relays​

Restricted access:

  • Whitelist-based
  • Often for communities
  • Maximum control
  • Custom policies

Relay Selection for Finance​

Critical Factors​

FactorImportanceWhy
UptimeCriticalPayments need delivery
RetentionHighHistorical data access
SpeedHighReal-time transactions
PrivacyMediumFinancial data sensitivity

Finance-Specific Considerations​

NWC Relays​

For Nostr Wallet Connect:

  • Reliability essential for payment flow
  • Fast message delivery
  • Good uptime record

Commonly used:

  • wss://relay.getalby.com/v1
  • wss://nostr.mutinywallet.com

Zap Receipts​

For zap receipt delivery:

  • Include multiple relays in requests
  • Use relays recipient is connected to
  • Check relay list in profiles

On-Chain Coordination​

For on-chain payments:

  • Publish PSBTs to trusted relays
  • Use encrypted messages for sensitive data
  • Ensure delivery confirmation

Running Your Own Relay​

Benefits​

  • Full control over your data
  • Guaranteed access to your events
  • Privacy from third parties
  • Custom policies

Options​

SoftwareLanguageFeatures
strfryC++High performance
nostreamTypeScriptFeature-rich
nostr-rs-relayRustConfigurable
relayGoSimple setup

Basic Setup (strfry)​

# Clone and build
git clone https://github.com/hoytech/strfry
cd strfry
make setup-golpe
make -j4

# Configure
cp strfry.conf myrelay.conf
# Edit configuration

# Run
./strfry relay

Relay Policies​

Event Filtering​

Relays can restrict:

  • Event kinds accepted
  • Pubkeys allowed
  • Content types
  • Event size

Rate Limiting​

Common limits:

  • Events per minute
  • Connections per IP
  • Bandwidth per user

Data Retention​

Policies vary:

  • Forever (rare)
  • Time-based (e.g., 90 days)
  • Size-based (newest kept)
  • Kind-based (some permanent)

Monitoring Relays​

Health Checks​

async function checkRelay(url) {
  try {
    const start = Date.now();
    const ws = new WebSocket(url);

    await new Promise((resolve, reject) => {
      ws.onopen = resolve;
      ws.onerror = reject;
      setTimeout(reject, 5000);
    });

    const latency = Date.now() - start;
    ws.close();

    return { status: 'up', latency };
  } catch {
    return { status: 'down', latency: null };
  }
}

Tools​

Best Practices​

For Users​

  1. Use multiple relays - Redundancy is key
  2. Include paid relays - Better reliability
  3. Test regularly - Ensure connectivity
  4. Backup data - Don't rely solely on relays

For Financial Apps​

  1. Retry logic - Handle failures gracefully
  2. Multiple paths - Write to several relays
  3. Confirmation - Verify event publication
  4. Timeouts - Don't wait forever

Example: Robust Publishing​

async function publishWithRetry(event, relays, maxRetries = 3) {
  const results = [];

  for (const relay of relays) {
    let attempt = 0;
    while (attempt < maxRetries) {
      try {
        await publishToRelay(event, relay);
        results.push({ relay, success: true });
        break;
      } catch (error) {
        attempt++;
        if (attempt === maxRetries) {
          results.push({ relay, success: false, error });
        }
        await sleep(1000 * attempt); // Exponential backoff
      }
    }
  }

  const successCount = results.filter(r => r.success).length;
  if (successCount === 0) {
    throw new Error('Failed to publish to any relay');
  }

  return results;
}

Resources​

Financial Reliability

For financial applications, relay reliability directly impacts user experience. Invest in good relay connections - a few dollars per month for paid relays is worthwhile insurance.