I'm working on a Magento2 with 100's of websites in a multi-store setup. We're presently not using the asynchronous indexing feature, but rather re-index in full once per day. The whole reindexing process takes about 1 hour.
It appears that Magento processes each store in sequence by store_id. That means, a store with a high id - e.g. 765 - will not get re-indexed until all the other ones are fully processed. This repeats for each individual indexer.
I would like to affect that sequence so that certain stores - let's say the most active ones - get processed first.
Pretty sure, I'm going to need to write a module for this, but I'm looking for help with where to tap into the execution chain to override the default behavior.