# event-id-missing

The request leaves out an **event ID**, such as that of a bound or an anchor.

- **Routes:** `write-events`, `read-events`, `observe-events`, `audit-history`, and `create-backup`
- **Description:** `event ID is missing: expected a non-negative integer of at most 9223372036854775807 in a string, such as '42'`
- **Details:** When reading or observing events, **`bound`**, the bound that leaves out its ID, `lowerBound` or `upperBound`. When writing events, **`precondition`**, the place of the precondition in its list, counting from 0. When auditing the history or creating a backup, none; `details` is an empty object.

## Why It Happens

Several requests name an event by its ID: the **`lowerBound`** and **`upperBound`** of a read, the `lowerBound` of an observation, the **`eventId`** of an `isSubjectOnEventId` **[precondition](/docs/eventsourcingdb/preconditions)**, and the **`id`** of the event that an **[audit](/docs/eventsourcingdb/auditing-the-event-store)** or a **[backup](/docs/eventsourcingdb/backup-and-restore)** continues from, in `lastAuditedEvent` or `lastBackedUpEvent`. The database reports this error when that ID is **left out or is an empty string**. A bound is checked for its ID before its type, so a bound that is an empty object reports this error.

A typical cause is an **empty object where `null` is meant**: a first audit or a full backup sends `null` as `lastAuditedEvent` or `lastBackedUpEvent`, while `{}` names an event without its ID.

## How to Fix It

Send the ID of the event as a non-negative integer in a string, without a sign or a leading zero, such as `"42"`, or, for a first audit or a full backup, `null` in place of the whole event. Sending the same request again fails the same way, since the error depends on the request alone.

## Example

To read the events of `/books/42` with a `lowerBound` that has a type but no ID, EventSourcingDB answers with this error, as a line of the stream, and then ends the stream with its `end` item:

```json
{
  "type": "error",
  "data": {
    "code": "https://docs.eventsourcingdb.io/errors/event-id-missing",
    "description": "event ID is missing: expected a non-negative integer of at most 9223372036854775807 in a string, such as '42'",
    "details": {
      "bound": "lowerBound"
    }
  }
}
```