Aurora Postgresql RDS DB Latency

Hi Postgres Team,
We are using AWS Aurora RDS Postgres DB 9.6.8 Engine. We recently deleted
few million rows from the database and ran into a issue in one of our dev
account where the
DB was not normal after this deletion. We did re index, vacuuming entire
database but we couldnt bring it to the same state as earlier. So next
steps we deleted the database and
recreated the database by copying the snapshot from a production instance.
Further did vacumming, re-index on the database.

After this now the dev database seems to be in a better state than earlier
but we are seeing few of our DB calls are taking more than 1 minute when we
are fetching data and we observed
this is because the query plan was executing a hash join as part of the
query whereas a similar query on prod instance is not doing any hash join
and is returning faster.

Also we did not want to experiment by modifing the DB settings by doing
enable_hash_join to off or random_page_count to 1 as we dont have these
settings in Prod instance.

Note:
The partition table sizes we have here is between 40 GB to 75 GB and this
is our normal size range, we have a new partition table for every 7 days.

Appreciate your ideas on what we could be missing and what we can correct
here to reduce the query latency.

Thanks
githubKran