> ## Documentation Index
> Fetch the complete documentation index at: https://documentation.debbiecollect.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Idempotency

> Ensuring safe retries with Idempotency Keys

The Debbie API supports idempotency for non-idempotent requests through the optional `Idempotency-Key` header. This ensures that retrying the same request multiple times will produce the same result, preventing duplicate operations.

## Using Idempotency Keys

* Include an Idempotency-Key header with a unique string (we recommend UUIDs)
* Maximum key length is 64 characters
* Keys are valid for 48 hours
* Responses served from the idempotency cache include an Idempotency-Cached header

## Example

```header theme={null}
Idempotency-Key: 123e4567-e89b-12d3-a456-426614174000
```

## Error Cases

* Invalid key format: 400 Bad Request
* Reusing a key for a different request: 400 Bad Request

## Best practices

* Use a new key for each unique business transaction
* Use the same key when retrying a failed request
* Store keys with request details for debugging