An event is a record that something has happened. It is a fact about the past. Events are immutable — once something happens, you can't un-happen it.

Real-world analogy: When you place an order on Amazon, the event OrderPlaced happens. Amazon doesn't delete that fact — it just moves forward from there.

Code Example (JSON event):

{
  "eventType": "OrderPlaced",
  "eventId": "evt-001",
  "timestamp": "2024-01-15T10:30:00Z",
  "data": {
    "orderId": "ord-123",
    "userId": "usr-456",
    "items": ["book", "pen"],
    "totalAmount": 29.99
  }
}

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