Milking Performance from Riak Search by Gary William Flake.
From the post:
The primary backend store of Clipboard is built on top of Riak, one of the lesser known NoSQLs solutions. We love Riak and are really happy with our experiences with it — both in terms of development and operations — but to get to where we are, we had to use some tricks. In this post I want to share with you why we chose Riak and also arm you with some of the best tricks that we learned along the way. Individually, these tricks gave us better than a 100x performance boost, so they may make a big difference for you too.
If you don’t know what Clipboard is, you should try it out. We’re in private beta now, but here’s a backdoor that will bypass the invitation system: Register at Clipboard.
Good discussion of term-based partitioning and its disadvantages. (Term-based partitioning being native to Riak.) Solved in part by judging likely queries in advance and precomputing inner joins. Not a bad method, depending on your confidence in your guesses about likely queries.
You will also have to determine if sorting on a primary key meets your needs, for a 10X to 100X performance gain.