Most operations are client side so you can model very quickly and the server catches up even if you are on slow connections.

Right now Boolean operations are also client side, this allows for things like this animated Boolean scene (press play):

http://clara.io/view/86e0579a-4dc8-4145-81a8-6ad9f765b30b

We may be introduce server side Boolean operations that are more robust, but less flexible. There is a limit to the complexity of the code we can run client side and the best Boolean algorithms are actually really complex/costly and thus hard to easily execute in the client.