When does operations go into queue

In the Lab: Building an Index in the Foreground in Production, the queries took longer time, after running building_index_in_foreground.py. Is it becuase during those operations are queried on mongo when index is being built? If so, i haven’t seen any of those operations going into the ‘qrw’ field in mongostat. If not so, when do operations go into the ‘qrw’?

please help me understand what happened there.

If you recall from the lectures, Foreground Index Builds will block all read/write operations on the collection. Which means that the index build must complete before any read/write operations on that collection can resume.

Suggest reviewing the following lectures: