Some MapReduce caveats
Tuesday, February 23, 2010
7:41 PM
MapReduce Caveats
Not everything is efficient to do via MapReduce.
Creating the datastore takes time. 
If data is not persistent, distribution might not be worth the trouble.
Example: searching real-time stock data.
Not every datastore is suited for every operation
Changing data format (via a Map) takes time and space. 
Sometimes the time taken to change format isn't worth it. 
Example: inverting a huge index <k,v> => <v,k> in order to search by v instead of k.