If you want ha then you’d configure postgres to replicate, and maybe redis as well, though it’s not a big problem to just start with a new redis.
There are guides about setting up postgres replication elsewhere. Or you could get rds to do it for you.
Then you’d configure two web_only containers (Move from standalone container to separate web and data containers.
You’d then need to have haproxy or something to handle the switch.
It’s really beyond the help you can get here unless cyou’re stuck on the discourse part of things.