How does indexes work on CB Lite

I have tried to found how does CB Lite indexes work on Sync Gateway document replication. But i couldn’t find any information on this topic.
I have and issue on android app. After initial replication application is a little bit unresponsive. After that I have kill application and started it again and it’s working just fine. I assume that first time indexer is working on indexes and second time, everything is already indexed.
Also is it any way to monitor indexer job on indexes ?

Couchbase Lite does not have async indexing. All of the indexing is done synchronously by the underlying engine. It either happens all at once when an index is added after documents, or the indexing happens per write when documents are added after an index. I think the performance hit is coming from somewhere else, but without some profiling there is no way to say where.

It’s weird that this happen on first synchronization from Sync Gateway and after that it’s work fine