On a mongo collection with 1.8 Million documents the following steps were taken:
> db.collection.dropIndexes()
> db.collection.ensureIndex() // ran this multiple times for the various indexes on it the collection

At this point the RPS of the application, and mongo's throughput were a quarter of what they were before the indexes were dropped and readded.
Then i ran a
> db.collection.reIndex()
Which brought the throughput and the RPS back up to the levels it was before the indexes were dropped.

What i wanted to know was is this expected behavior, and is it recommended to run a reIndex after an index is added to an existing collection.