Get the Replication/Lag time of Redshift
In this context, I usually create a specific table to see the last replication status.

On your PostgreSql master server, you create a simple table, example:

CREATE TABLE check_replication ( now_date timestamp );


Then you create a batch or job, that performs every minute, or more often:

INSERT INTO check_replication ( now_date ) VALUES (now());


Then, you add this table in the replicated tables from PostgreSql to RedShift

And you can check the replication delay.

HTH,
Thomas