Thanks for the feedback guys.
I guess what I want to say, in short, is the question should probably be "Do you really need to read/write to the database all the time, or can you just use it as a bucket where you pull starting state from?".
What would be a "good" strategy for dumping stuff into that bucket?
In the Joe Armstrong example of if he were to rewrite Twitter today, he would have each user and each tweet be a process. How often would have the app dump tweets into the database at a set interval?
The Phoenix app...SORRY Elixir app .. that I started on was a Home brewing app. I had users, recipies that consisted of malt profiles, yeasts, hops and so on. All of these things can be represented as prosesses and communicate via messaging. A batch of a given recipe would have a brewdate and so forth. Everything is fine (hopefully), until the server crashes.
So is the only question how vulnerable the app is to data loss?