Feedback on load balancing with app and db on same server

Wondering if I can get feedback on better deployment strategies.

I’m a beginner at elixir/phoenix deployment and successfully deployed a small production project with the app and db on the same server (DO droplet).

However, I’m wanting to test a better deployment strategy with high availability.

Is it OK to have an active-active cluster of 2 droplets, where each droplet server has an app and db instance? Would one of the databases need to be passive (failover)?

for example:

DO Load balancer sends request to:

active app1. active db1
active app2. passive db2 (failover).

Can someone provide link to guides on simple HA deployment strategies (1 or 2 load balancers*, 2 app servers and 2 db servers)?

*based on DO’s documentation, their load balancers already have HA. Thus, 1 could suffice I assume.