The number of partitions is fixed at the time of the index creation. Each partition is an indivisible chunk of data which can grow in size but not be split into smaller chunks. As the data grows, more nodes may be added to the cluster, but the number of partitions which eventually move to the newer nodes are limited (Fig 3)
ZEBRAs think they know it all but rely on their opinion rather than any actual evidence. To stave off the ZEBRAs in your midst, make sure that you’ve got data to back up your decisions. Come up with quick experiments you can run to test ideas and gather evidence.