Supporting distributed key-based processes is described. In an embodiment, servers at a data center provide a key-based process for carrying out computationally expensive tasks and are connected using point to point connections in a geometric topology such as a torus. In an example, aggregation trees are built on top of the geometric topology of the data center, each aggregation tree being a sequence of servers in the data center that forms a tree structure. In an embodiment packets of data are sent from the leaves of the trees to the root and at each server along the tree the packets are aggregated using a combiner function of the key-based process. In an embodiment, if a server fails, the trees are dynamically recomputed and a recovery phase is triggered to resend any packets lost at the failed server. In some embodiments, packets are scheduled by inspecting the content of the packets.