How to see an explain sql for a fetchCount

I have a query that is taking a pretty long time to do a fetchcount with a filter (13 seconds), yet a fetch using an order and an index only takes 0.3 seconds, so trying to understand how the fetchCount is working.

The fetchCount on the entire table only takes 1.5 seconds. This subset of the table is 25-30% of the record count of the entire set.

Any ideas? or is splunk needed for this.

Thanks

Can use an evaluate with a projection of count() and the same filter, then add explain: true to spec.