To add to 030's answer, and as a devops engineer who has had to do this a few times, learning how to set up replication and failover in an automated fashion is very important.
If you're learning, start by setting up replication by hand on some test servers
Then craft a method for automating ...
In my opinion an Operations candidate (DevOps is a culture, not a role) should be capable to perform at least the following actions:
run some psql commands like select and some innerjoins
knows what the effect on memory usage would be if a select * is issued
No manual labour, only automation. Deploy the ...