Ah I see what you're saying! You're basically describing our experience trying to run Discourse. Weirdly, naive, less complicated Rails apps work better multi-region on Fly than mature grownup Rails apps.
We use sidekiq + Fly in a single region with the primary database, and then write to the Redis from other regions asynchronously. It's a good time in Ruby world, I think Ruby 3 will simplify a lot of the weird background work people do.
Ruby 3 will definitely help us solve the problem of gets that do writes for stats or history, since those things can be done async. You can do a little of it now just by spawning a thread and writing the the writable Postgres in the background.
