In Kafka Streams, the StateRestoreCallback interface provides only a single method "restore(byte key, byte value)" that is called for every key-value pair to be restored.
It would be nice to have "beginRestore" and "endRestore" methods as part of StateRestoreCallback.
Kafka Streams would call "beginRestore" before restoring any keys, and would call "endRestore" when it determines that it is done. This allows an implementation, for example, to report on the number of keys restored and perform a commit after the last key was restored. Other uses are conceivable.