1. A method comprising the following steps: determining one or more dimensions of a set of containers in which multiple tasks associated with a request are to be executed; assigning each container in the set of containers (i) to a processing node on one of multiple platforms based on the determined one or more dimensions of the given container, and (ii) to a platform owner selected from the multiple platforms based on a comparison of one or more resource requirements of each of the multiple platforms and the determined one or more dimensions of the given container; and generating container assignments across the set of containers for the multiple tasks associated with the request, wherein said generating comprises incorporating (i) the assigned node of each container in the set of containers, (ii) the assigned platform owner of each container in the set of containers, (iii) one or more scheduling requirements of each of the multiple platforms, and (iv) one or more utilization objectives, and wherein said generating further comprises enforcing a sharing guarantee of each of the multiple platforms; wherein said steps are carried out by a computing device.