We have a very heavy load in Read side with large DB tables in 2 hours per day that affect to Db so as solutions I have created read replica for it.
If application fetches large heavy data on read replica, is MasterDB affect with that havy load or it will work as it is.
Replication Lag is key for it also Of, if you huge select will affect the master when you have MyISAM in place. But Aurora completely designed with InnoDB. So it won't.
The thread is available here
https://dba.stackexchange.com/questions/211976/are-read-replicas-heavy-reading-in-affect-masterdb