Thanks, @codinghorror and @mpalmer for taking the time to write me a thoughtful reply. I appreciate your time is limited, and I’m grateful for the time you took, and assistance you offered.
@mpalmer your suggestion to run only the app in Docker is inline with my own thinking. I have some limited experience with running RoR apps in production, and it wasn’t all nice 
I don’t have an issue running Redis (we already have a cluster for a few other things) and pg also won’t be too much of a problem.
I would also like to get some kind of idea of initial resource required. I really appreciate that this is dependent from site to site, and that I will have to find my own balance somewhere along the line, but I’d like to get some kind of idea of how to spec initially. I don’t really want to over or underprovision too much. Let me rephrase my question. Assuming a 4GB DigitalOcean host for the DB, and a similar gaggle of hosts running Redis, what kind of appservers would I need to run the app, allowing for about 300 posts in a 16 hour window? I’d have at least 3 behind HAProxy,