1. A method comprising: identifying node requirements of a first tier of a plurality of tiers wherein each tier of the plurality of tiers has a different computing function; retrieving attributes of a set of computing nodes, each node of the set of computing nodes comprising a processor; comparing the attributes of the set of computing nodes to the node requirements of the first tier; calculating a processing energy for each node of the set of computing nodes based on differences between the attributes of the set of computing nodes and the node requirements of the first tier; selecting at least one node of the set of computing nodes having a lowest positive processing energy; and assigning the selected at least one node to at least one node slot of the first tier.