When consumers read from a partition, they also commit an offset to remember the position they last read in the partition. We’ll cover commits and offsets in depth later. When a consumer can’t find a valid offset, (which can happen if the consumer is down for long enough for the record pointed to by the last committed offset to age out), the consumer can choose to start reading records in the partition from the beginning or from the newest record. The configuration auto.offset.reset controls this behavior to read earliest or newest records when a valid offset can’t be determined for a partition.