Option C provides the best approach to guarantee idempotency. Creating a temporary table, writing the data to it, and then atomically renaming it ensures that the table is either fully updated or remains in its original state. If failures happen after the creation of temporary table and before it is renamed (a failure which is assumed to be very rare), then, after code recovery and execution, the table would be first created and then atomically renamed, thus achieving idempotency. Retrying writes (B) can help with network errors but doesn't inherently guarantee idempotency if the write partially succeeds before the error. 'append' (A) leads to duplicate data in the event of re-execution. 'MERGE (D) might lead to data inconsistency depending on the transformation logic. 'TRANSACTIONAL REPLICATION' (E) is a good approach for disaster recovery but will not help to resume the execution, after recovering the code after failure, at the point where it failed before.