Postgres and NodeBalancer - possible?

I have no experience with Postgres or NodeBalancer, and I was wondering if what I'm picturing in my head is possible, or if I have a fundamental misunderstanding of any of the technologies involved.

Here's what I imagine: two servers running Postgres. Both are "masters" - can receive write and read queries. Each one replicates the write queries they receive to the other server.

Our apps point their DB address to NodeBalancer, which directs the traffic to one of the two servers. If one happens to go down, NodeBalancer will only direct traffic to the remaining one.

Is this a right-headed understanding of the possibilities of Postgres and NB, or am I wrong in thinking this setup is possible?