Majority of the applications are purely stateless, for a very few and apps we had to use either a shared volume/storage or simply locking to a specific node.

Majority of the applications are purely stateless, for a very few and apps we had to use either a shared volume/storage or simply locking to a specific node. We did first locking to specific node, but later decided to use s3fs for those kind of needs. Never needed the shared storage critically to setup anything heavy-lifting reliable. Although worth noting, from the beginning I had psql running within docker swarm as well, but it was locked to 1 node only, we had a good backup solution to spin up (tried it too) on another node quickly as well. With mode nodes in the cluster, I made the PSQL into its own machine completely separated from docker environment.