In situations where Map/Reduce is used and the value is not (always) needed at the Mapper, the value could be loaded lazy, when the map(..) interface is slightly changed:

map(Entry<KIn, VIn> entry, Collector<Entry<KIn, VIn>> collector)

When entry.getValue() is called, the value should be loaded from store or maybe remote node.

Maybe this change to Entry would be also useful for event api ISPN-1802