Fetches the original transaction response by the idempotency key used during the POST /v2/transaction request.

Security Behavior

To prevent information leakage, this endpoint returns an empty object {} in all negative cases — including when the idempotency key does not exist and when the key exists but belongs to a different merchant. Callers cannot distinguish between the two scenarios.

Loss of Reference Behavior

The idempotency key can reference the transaction only until the TTL expires. The current TTL is 1 day. After that, the transaction may exist but cannot be retrieved by the idempotency key.