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Scheduler

Scheduler → Function

Run a one-off task at a specific time (e.g. send email in 1 hour).

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The Pattern

Scheduler Function

Why this pattern?

  • One-time execution: No recurring cron — runs once at the given time
  • Timezone support: Schedule in any timezone
  • Payload: Pass context (user, order, type) so the function knows what to do
  • Use cases: Reminders, delayed notifications, "cancel if no payment" flows
Example implementation
// Schedule a one-off task (e.g. "send reminder in 1 hour")
const inOneHour = new Date(Date.now() + 60 * 60 * 1000).toISOString()

await fetch('https://api.rocketstack.dev/schedules', {
  method: 'POST',
  headers: {
    'Authorization': 'Bearer YOUR_API_KEY',
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({
    name: 'reminder',
    runAt: inOneHour,
    deliveryTarget: {
      type: 'function',
      functionId: 'fn_send_reminder'
    },
    payloadTemplate: {
      userId: 'usr_123',
      type: 'payment_reminder',
      orderId: 'ord_456'
    }
  })
});

// Your Function runs once at the scheduled time
// fn_send_reminder
export default async function handler(event) {
  const { userId, type, orderId } = event.payload;

  if (type === 'payment_reminder') {
    const user = await getUser(userId);
    await sendEmail(user.email, {
      subject: 'Complete your purchase',
      body: `Your order ${orderId} is waiting. Complete payment within 24h.`
    });
  }

  return { sent: true };
}
More examples Webhook → Queue → Function Cron → Function → KV Storage → Queue → Function KV session or cache
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