Supabase Realtime Connection Issues - AI-Optimized Reference

Configuration: Production-Ready Settings

Critical Library Versions

• Use: @supabase/supabase-js@2.50.0
• Avoid: v2.50.1 (critical connection failures documented in GitHub #36641)
• Minimum: @supabase/realtime-js@2.10.7

Database Connection Configuration

const supabase = createClient(supabaseUrl, supabaseKey, {
  db: {
    schema: 'public',
  },
  auth: {
    persistSession: false, // Prevents connection hoarding
  },
  realtime: {
    params: {
      eventsPerSecond: 10, // Rate limiting prevents flooding
    },
  },
});

// REQUIRED for server routes: Add ?pgbouncer=true
const pooledConnectionString = `postgresql://postgres:[PASSWORD]@db.[REF].supabase.co:6543/postgres?pgbouncer=true`;

RLS Policies for Realtime Compatibility

-- Standard policy for app users
CREATE POLICY "Users see own data" ON messages
  FOR SELECT USING (auth.uid() = user_id);

-- CRITICAL: Additional policy for realtime service
CREATE POLICY "Realtime service access" ON messages
  FOR SELECT USING (
    auth.role() = 'authenticated' -- App users
    OR auth.role() = 'service_role' -- Realtime server
  );

-- Enable realtime on table
ALTER PUBLICATION supabase_realtime ADD TABLE messages;

Resource Requirements

Connection Limits by Tier

• Free Tier: 200 connections maximum
• Pro Tier: 500 connections maximum
• Critical Threshold: 180+ active connections indicates imminent failure

Mobile Reconnection Implementation Cost

• Development Time: 2-3 hours for proper handling
• Complexity: Moderate (requires app lifecycle management)
• Maintenance: Ongoing testing required for iOS/Android updates

Production Monitoring Setup

• Initial Setup: 4-6 hours
• Tools Required: Database monitoring, connection pool tracking, error alerting
• Expertise Level: Intermediate database administration knowledge

Critical Warnings

Connection Pool Exhaustion

Failure Mode: "Unable to connect to database" error

• Root Cause: Exceeding connection limits (200 free, 500 pro)
• Detection: Monitor pg_stat_activity table
• Impact: Complete application failure under load
• Prevention: Enable connection pooling with ?pgbouncer=true

-- Monitor connection usage (run regularly)
SELECT count(*) as active_connections, state 
FROM pg_stat_activity 
WHERE datname = current_database()
GROUP BY state;

Mobile Background Connection Kills

Failure Mode: WebSocket connections die when app goes background

• Affected Platforms: iOS and Android (battery optimization)
• Recovery Time: 3-5 seconds if handled properly, infinite loop if not
• User Impact: Lost real-time updates, reconnection loops

Required Implementation:

private handleVisibilityChange = () => {
  if (document.visibilityState === 'visible' && !this.channel) {
    this.connectWithBackoff();
  } else if (document.visibilityState === 'hidden') {
    this.disconnect(); // Prevent OS from killing connection ungracefully
  }
};

RLS Policy Blocking

Failure Mode: CHANNEL_ERROR status with no error details

• Root Cause: RLS policies block realtime service differently than app queries
• Detection: Subscription shows SUBSCRIBED but no data flows
• Debug Method: Test with permissive policy temporarily

Version-Specific Failures

Critical Versions:

• supabase-js@2.50.1: Connection pool exhaustion bug
• realtime-js < 2.0.0: Concurrent subscription conflicts

Implementation Reality

Reconnection Pattern That Actually Works

class RealtimeManager {
  private channel: RealtimeChannel | null = null;
  private reconnectAttempts = 0;
  private maxReconnectAttempts = 5;
  
  connect(userId: string) {
    // CRITICAL: Remove old channel completely
    this.disconnect();
    
    this.channel = supabase
      .channel(`user:${userId}`)
      .on('postgres_changes', {
        event: '*',
        schema: 'public',
        table: 'messages',
        filter: `user_id=eq.${userId}`
      }, (payload) => {
        this.reconnectAttempts = 0; // Reset on successful data
      })
      .subscribe((status) => {
        switch (status) {
          case 'CHANNEL_ERROR':
            console.error('RLS policies likely blocking realtime');
            this.handleConnectionError();
            break;
          case 'TIMED_OUT':
            console.error('Network issues or server overload');
            this.handleConnectionError();
            break;
        }
      });
  }
  
  private disconnect() {
    if (this.channel) {
      supabase.removeChannel(this.channel); // Essential cleanup step
      this.channel = null;
    }
  }
}

Default Settings That Fail in Production

• Auto-reconnection: Not implemented by default, must build custom
• Connection pooling: Disabled by default, causes pool exhaustion
• Mobile lifecycle: No handling provided, requires manual implementation
• Error boundaries: No built-in fallback, app crashes on connection failures

Hidden Costs

• Development Time: 6+ months to handle all edge cases properly
• Monitoring Setup: Requires database expertise and alerting infrastructure
• Mobile Testing: Must test on physical devices, simulators insufficient
• Version Management: Manual testing required for each library update

Failure Scenarios and Consequences

Corporate Firewall Blocking

Impact: Complete WebSocket failure in enterprise environments
Detection: WebSocket upgrade fails, falls back to polling (if implemented)
Workaround: HTTPS-only connections, no reliable solution for strict firewalls

Network Switching (Mobile)

Impact: Connection drops during cell tower handoffs, WiFi transitions
Recovery: 5-30 seconds if exponential backoff implemented
User Experience: Appears as temporary freezing of real-time features

Server-Side Connection Limits

Impact: New connections rejected, existing connections may be killed
Cascade Effect: Users refresh page, making problem worse
Recovery: Requires connection pool configuration and monitoring

Debugging Decision Tree

Connection Status: SUBSCRIBED but No Data

1. Check RLS policies: Test with permissive policy
2. Verify publication: Ensure table added to supabase_realtime
3. Test direct query: Confirm data access with same user token

Connection Status: CHANNEL_ERROR

1. RLS Policy Issue (90% of cases)
2. Invalid JWT token (expired or malformed)
3. Table not in publication (missing ALTER PUBLICATION)

Connection Status: TIMED_OUT

1. Network connectivity issues
2. Server overload (check Supabase status page)
3. Connection pool exhaustion (monitor active connections)

"Unable to Connect to Database"

1. Connection pool full (immediate priority)
2. Database maintenance (check status page)
3. Invalid connection string (verify environment variables)

Operational Thresholds

Connection Health Monitoring

• Green: < 150 active connections (free tier), < 400 (pro tier)
• Yellow: 150-180 connections (free), 400-450 (pro) - implement alerting
• Red: > 180 connections (free), > 450 (pro) - immediate intervention required

Reconnection Backoff Strategy

const backoffDelay = Math.min(1000 * Math.pow(2, reconnectAttempts), 30000);
// Results: 1s, 2s, 4s, 8s, 16s, 30s (capped)

Error Rate Thresholds

• Acceptable: < 5% connection failure rate
• Warning: 5-15% failure rate - investigate causes
• Critical: > 15% failure rate - disable realtime, use fallback polling

Migration and Breaking Changes

Known Breaking Changes by Version

• v2.50.0 → v2.50.1: Connection pool handling changed (regression)
• v2.0.0: Channel subscription API changed, requires code updates
• v1.x → v2.x: Complete rewrite, no backward compatibility

Safe Update Strategy

1. Check GitHub issues for target version
2. Test in staging with real connection loads
3. Monitor error rates for 48 hours post-deployment
4. Prepare rollback plan with previous version pinned

Architecture Patterns

Resilient Realtime Implementation

class DataManager {
  private isRealtimeActive = false;
  
  async initializeData() {
    // Always load via REST first
    const initialData = await this.fetchDataViaREST();
    this.updateUI(initialData);
    
    // Try realtime enhancement
    this.startRealtime();
    
    // Setup polling fallback
    this.setupFallbackPolling();
  }
  
  private setupFallbackPolling() {
    setInterval(async () => {
      if (!this.isRealtimeActive) {
        const data = await this.fetchDataViaREST();
        this.updateUI(data);
      }
    }, 10000); // 10-second polling when realtime fails
  }
}

Error Boundary Implementation

class RealtimeErrorBoundary {
  private errorCount = 0;
  private maxErrors = 5;
  private cooldownPeriod = 300000; // 5 minutes
  
  shouldAttemptConnection(): boolean {
    const now = Date.now();
    if (this.lastError && now - this.lastError > this.cooldownPeriod) {
      this.errorCount = 0; // Reset after cooldown
    }
    return this.errorCount < this.maxErrors;
  }
}

Performance Impact

Client-Side Resource Usage

• Memory: ~50KB per active channel subscription
• CPU: Minimal during normal operation, spikes during reconnection storms
• Battery: Significant on mobile when handling frequent reconnections

Server-Side Resource Impact

• Connection Overhead: Each WebSocket consumes 1 database connection
• Memory per Connection: ~8KB server-side
• CPU Impact: Increases with message frequency and subscriber count

Support Quality Assessment

Official Support Channels

• Documentation: Good for basic setup, lacks troubleshooting depth
• GitHub Issues: Active responses, 2-7 day response time
• Discord: Real-time help available, community-driven
• Enterprise Support: Available for Pro/Team tiers only

Community Resources Quality

• Stack Overflow: Limited Supabase-specific content
• Reddit: Mixed quality, mostly basic questions
• GitHub Discussions: Best source for production issue solutions
• Medium/Blog Posts: Often outdated, verify versions before following

Known Support Gaps

• Complex RLS debugging: Limited official guidance
• Mobile-specific issues: Community-driven solutions mostly
• Performance optimization: Requires reading source code
• Version compatibility: Must track GitHub issues manually