[ChristianMarks]

I can think of one case where a redis dictionary is used to represent a tree, and reductions are needed over a subtree. Calculations on river networks are like this. You might want to use redis instead of a cPickled dictionary, and you might not want the overhead of a full Hadoop.

[sitkack]

On redis 2.6 you can use Lua, reductions over lists could be done directly on the server.