Idempotency keys

Networks fail. An idempotency key lets you retry a send without risking a duplicate.

Send any unique string up to 256 characters in the Idempotency-Key header. Postwick remembers it for 24 hours; a second request with the same key returns the first response instead of sending again.

await postwick.emails.send(payload, { idempotencyKey: `welcome/${user.id}` });

curl https://api.postwick.dev/emails \
  -H "Idempotency-Key: welcome/8812" \
  -H "Authorization: Bearer $POSTWICK_API_KEY" \
  -d @payload.json