As illustrated in scene 106, a replacement data consumer, replacement data consumer 130, may take over processing of data records from data stream partition 100. Replacement data consumer 130 may first obtain 132 partition checkpoint metadata 120. Based on the partition checkpoint metadata 120, replacement data consumer 130 may determine whether or not the data records retrieved at 112 were emitted. In this way, data records may be processed idempotently so that the data records are only delivered to a destination once. For example, an intention marker, record, or other indicator included in the update 114 to checkpoint metadata may be evaluated to detect whether the data records were emitted. A key-value store, for instance, that maps a stored data value to a unique key, may be the destination for data records emitted from data consumer 130. The checkpoint metadata may include a key value that is intended to be paired with the data record(s) emitted. Replacement data consumer 130 may send a request to the key-value store to check to see if the key exists, and if so, then it may be determined that the data records were already delivered to the key-value store. If, however, the key does not exist, then it may be determined that the data records were not delivered. Note that such a determination may be performed differently according to the destination to which the data records are bound or the marker indicator, or record included in partition checkpoint metadata to indicate the intention to process records.