scan-cap <=0 makes it default value 512. DOC-3795
Set high value. cc @deepkaran.salooja is there any way disable backfill from indexer side.
In 5.5 https://developer.couchbase.com/documentation/server/5.5/settings/cluster-settings.html
Query Temp Disk Path Quota 0 makes it disable
Check system:completed_requests for high PhaseCounts for IndexScan
https://dzone.com/articles/query-performance-monitoring-made-easy-with-couchb