If I understand correctly, Amazon Aurora has asynchronous read replica. So, we can get some read lag (it seems, lag is about 100 ms).
I need synchronous read replica. So, can I set such type of replicate for Amazon Aurora for PostgreSQL?
Sorry but you can't change Aurora Replication type, Aurora is Amazon Aurora has asynchronous read replica but the lag isn't a major problem normally it is just a few milliseconds, not all the time 100 ms.
For additional information please refer to https://aws.amazon.com/rds/aurora/faqs/