Idempotency semantics

Idempotency prevents duplicate messages when clients retry POST requests.

How to use it

1. Generate a unique Idempotency-Key per logical send.
2. Reuse the same key for retries of the same request.
3. Do not reuse the key for different payloads.

When to use it

• Network timeouts
• 429 responses with Retry-After
• Client retries after transient failures