Inngest Events

# Inngest Events

Master Inngest event design and delivery patterns. Events are the foundation of Inngest - learn to design robust event schemas, implement idempotency, leverage fan-out patterns, and handle system events effectively.

> **These skills are focused on TypeScript.** For Python or Go, refer to the [Inngest documentation](https://www.inngest.com/llms.txt) for language-specific guidance. Core concepts apply across all languages.

## Event Payload Format

Every Inngest event is a JSON object with required and optional properties:

### Required Properties

```typescript
type Event = {
  name: string; // Event type (triggers functions)
  data: object; // Payload data (any nested JSON)
};
```

### Complete Schema

```typescript
type EventPayload = {
  name: string; // Required: event type
  data: Record<string, any>; // Required: event data
  id?: string; // Optional: deduplication ID
  ts?: number; // Optional: timestamp (Unix ms)
  v?: string; // Optional: schema version
};
```

### Basic Event Example

```typescript
await inngest.send({
  name: "billing/invoice.paid",
  data: {
    customerId: "cus_NffrFeUfNV2Hib",
    invoiceId: "in_1J5g2n2eZvKYlo2C0Z1Z2Z3Z",
    userId: "user_03028hf09j2d02",
    amount: 1000,
    metadata: {
      accountId: "acct_1J5g2n2eZvKYlo2C0Z1Z2Z3Z",
      accountName: "Acme.ai"
    }
  }
});
```

## Event Naming Conventions

**Use the Object-Action pattern:** `domain/noun.verb`

### Recommended Patterns

```typescript
// ✅ Good: Clear object-action pattern
"billing/invoice.paid";
"user/profile.updated";
"order/item.shipped";
"ai/summary.completed";

// ✅ Good: Domain prefixes for organization
"stripe/customer.created";
"intercom/conversation.assigned";
"slack/message.posted";

// ❌ Avoid: Unclear or inconsistent
"payment"; // What happened?
"user_update"; // Use dots, not underscores
"invoiceWasPaid"; // Too verbose
```

### Naming Guidelines

- **Past tense:** Events describe what happened (`created`, `updated`, `failed`)
- **Dot notation:** Use dots for hierarchy (`billing/invoice.paid`)
- **Prefixes:** Group related events (`api/user.created`, `webhook/stripe.received`)
- **Consistency:** Establish patterns and stick to them

## Event IDs and Idempotency

**When to use IDs:** Prevent duplicate processing when events might be sent multiple times.

### Basic Deduplication

```typescript
await inngest.send({
  id: "cart-checkout-completed-ed12c8bde", // Unique per event type
  name: "storefront/cart.checkout.completed",
  data: {
    cartId: "ed12c8bde",
    items: ["item1", "item2"]
  }
});
```

### ID Best Practices

```typescript
// ✅ Good: Specific to event type and instance
id: `invoice-paid-${invoiceId}`;
id: `user-signup-${userId}-${timestamp}`;
id: `order-shipped-${orderId}-${trackingNumber}`;

// ❌ Bad: Generic IDs shared across event types
id: invoiceId; // Could conflict with other events
id: "user-action"; // Too generic
id: customerId; // Same customer, different events
```

**Deduplication window:** 24 hours from first event reception

See **inngest-durable-functions** for idempotency configuration.

## The `ts` Parameter for Delayed Delivery

**When to use:** Schedule events for future processing or maintain event ordering.

### Future Scheduling

```typescript
const oneHourFromNow = Date.now() + 60 * 60 * 1000;

await inngest.send({
  name: "trial/reminder.send",
  ts: oneHourFromNow, // Deliver in 1 hour
  data: {
    userId: "user_123",
    trialExpiresAt: "2024-02-15T12:00:00Z"
  }
})