PostgregSQL Interview questions

If anything is changed in Postgresql configuration file how the changes are reflected ? And how to know if we need to restart or reload?
What is being sent during replication from primary to standby?
What is WAL ?
How you handled performance issues in your previous project ?
What are the parameters used to set Autovacuum ?
How many databases have you handled ?
What was the flavor of postgres used in your previous project ?
What is synchronous and asynchronous replication? What is the drawback of it ?
How is patching done?
Have you monitored alerts ? And what all alerts have you monitored ?
When replication was done how the standby was changed ? is it manually ?
How the standby is selected in EFM ?
For one primary how many standby servers you had ?