I read through this discussion and was very helpful:
However, we have a situation where we cannot let the index have deleted items. The reason is that we need the index to represent the state of HCP objects and not keep growing, and growing, and growing over time. This last point is important.
The situation is that content will be ingested into a "local" HCP that is small. Then will be "promoted" to another HCP that is larger; thus removed from the local HCP. HCI will be used to index the content (amongst other things) for the local content. Over a span of a long period of time, that would mean the local HCI index will outgrow its installation base.How can we accomplish this even with perhaps advanced index configuration?