Delivery Guarantees

T+0s:     Initial delivery → Failed (500 error)
T+5s:     Retry 1 → Failed
T+25s:    Retry 2 → Failed
T+2m:     Retry 3 → Failed
T+10m:    Retry 4 → Failed
T+50m:    Retry 5 → Failed
T+4h:     Retry 6 → Failed
T+10h:    Retry 7 → Failed
T+16h:    Retry 8 → Failed
T+22h:    Retry 9 → Failed
T+28h:    Retry 10 → Failed
T+34h:    Retry 11 → Failed
T+40h:    Retry 12 → Failed
T+46h:    Retry 13 → Failed
T+48h:    Final retry → Failed
          ↓
          Job discarded (exceeded 48-hour window)

import { db } from './database';

async function handleWebhook(req, res) {
  const { event_id, event_type, payload } = req.body;

  // 1. Check if we've already processed this webhook
  const existing = await db.query(
    'SELECT id FROM processed_webhooks WHERE event_id = $1',
    [event_id]
  );

  if (existing.rows.length > 0) {
    console.log(`Webhook ${event_id} already processed - ignoring duplicate`);
    return res.status(200).json({ status: 'already_processed' });
  }

  // 2. Process the webhook within a transaction
  try {
    await db.query('BEGIN');

    // Process the event
    if (event_type === 'user.created') {
      await db.query(
        'INSERT INTO users (id, email) VALUES ($1, $2)',
        [payload.user_id, payload.email]
      );
    }

    // 3. Mark as processed (prevents duplicates)
    await db.query(
      'INSERT INTO processed_webhooks (event_id, processed_at) VALUES ($1, NOW())',
      [event_id]
    );

    await db.query('COMMIT');

    // 4. Always return 2xx on success
    res.status(200).json({ status: 'processed' });
  } catch (error) {
    await db.query('ROLLBACK');

    // 5. Return 5xx for retryable errors
    console.error('Failed to process webhook:', error);
    res.status(500).json({ error: 'Processing failed' });
  }
}