[houseabsolute]

I'm also wondering why this kind of intervention is necessary at all. The NoSQL solution we use at work has load based automatic splitting, and I'd have thought (though I haven't confirmed) that this would be an obvious feature to include.

[mcfunley]

I would speculate that it's a poorly-chosen shard key. MongoDB's built-in sharding uses range-based indexing. If you choose user_id as your shard key, and those are autoincrementing integers, then you're screwed if newer users tend to be more active on average than older ones.

[jrockway]

Wait, people shard on a key other than something approximately random, like an sha1 hash!?

[dmytton]

Load based splitting is on the MongoDB roadmap, but doesn't exist yet.

[fizx]

Just because the feature exists, doesn't mean it works.

[icey]

Which NoSQL store do you use?

[houseabsolute]

http://labs.google.com/papers/bigtable.html