The index region and async event queue will be restored with its colocated data region's buckets. So during failover the new primary should be able to read/write index as usual.
Aggregation
In the case of partitioned regions, the query must be sent out to all the primaries. The results will then need to be aggregated back together. Lucene search uses FunctionService to distribute query to primaries.
Input to primaries
Serialized Query
CollectorManager to be used for local aggregation
Result limit
Output from primaries
Merged collector created from results of search on local bucket indexes.