Replying the nested comment, my current approach is to put multiple Ghost installations on one big AWS server. Each Ghost installation has its own codebase and

Replying the nested comment, my current approach is to put multiple Ghost installations on one big AWS server. Each Ghost installation has its own codebase and database, so they're very independent of each other, with upgrades and migrations all happening independently. Dunno if you'd call that single or multi tenant, but that's the gist. I can automate the upgrades and migrations and running them for all the installations at the same time, or leave your installation alone until you ask for an upgrade / migration.