# Retries and idempotency

Send an **`Idempotency-Key`** header (1 to 200 characters) on any write you may retry:

| What happens | Answer |
|---|---|
| The same key + the same body, within 24 h | The **first** answer again, with `"replayed": true`, never charged twice |
| The same key + a different body | `409` |
| The first request with this key is still running | `409` (retry shortly) |
| The first request failed | Nothing is remembered: the retry runs again |

- Scope: for saves (`/v1/memories`, `/v1/events`, `/v1/feedback`, `/v1/imports`) a key is per **memory space**. For every other write, it is per **credential** (another key's same `Idempotency-Key` is a separate request).
- Saves are also de-duplicated by content: the same record saved twice is one record.