This Splunk REST query will return KV Store Metrics:
| rest /services/server/introspection/kvstore/collectionstats | mvexpand data | spath input=data | rex field=ns "(?<App>.*)\.(?<Collection>.*)" | eval dbsize=round(size/1024/1024, 2) | eval indexsize=round(totalIndexSize/1024/1024, 2) | stats first(count) AS "Number of Objects" first(nindexes) AS Accelerations first(indexsize) AS "Acceleration Size (MB)" first(dbsize) AS "Collection Size (MB)" by App, Collection