This image shows the high-level workflow for adding a shard and redistributing chunks. There are three rows of shards shown.
In the first row, there are three existing shards, each with 4 chunks, and one new shard with no chunks in it.
In the second row, one chunk from each of the existing shards is shown selected and arrows point to the new shard, indicating that they will be moved there.
In the third row, each of the four shards has three chunks in it.