X_IDEMPOTENCY_RESERVATION_LOST

an idempotent action's reservation was taken over before its transaction could settle it

postgresIdempotencyStore, settling inside the handler's transaction. The call ran past the request deadline (the app's requestTimeoutMs) with its record still in flight, a retry under the same Idempotency-Key reclaimed the key, and this attempt's settlement then matched no row. The refusal rolls this attempt's transaction back, so the write is applied by the retry and never twice

resend this request with the same Idempotency-Key — the attempt that took the key over answers it, and this one's transaction was rolled back