# Errors and rate limits
Source: https://nordvec.com/cs/docs/guides/errors-and-rate-limits#retrying-writes-safely

## Retrying writes safely [#retrying-writes-safely]

A write operation that lists an `Idempotency-Key` header in the
[API reference](/docs/api) can be retried without doing the work twice. Send
one key per logical write and repeat the same key on every retry:

* the same key with the same body within 24 hours replays the stored response;
* the same key with a different body is refused with `422`;
* a duplicate that arrives while the first is still running gets `409`.

An operation without the header is not idempotent, so retry it only when you
know the first attempt did not land.