== Kafka: the log is the storage ==

group replay-group-1, first read           : 12 records
group replay-group-2, brand new group      : 12 records
group replay-group-1, after seekToBeginning: 12 records

Consuming does not remove anything. A consumer group is a cursor over a log
that the broker keeps until retention expires, so a new group, a reset
offset or a seek all read the same records again.