Scaling isn't so much the problem, since you can do various things to keep users on specific servers. In my setup, I also solve a lot of the state issues since

Scaling isn't so much the problem, since you can do various things to keep users on specific servers. In my setup, I also solve a lot of the state issues since there isn't a single state for the entire app, but instead for each process that runs a small part of the app. That means you can scale and change up the application easier if you need without impacting the other parts. The real problem with coroutines for storing state is simply that upgrading the code requires you to either kill all the old state, or trickle users off on A/B paired processes. Because the state is tied to the code, you can't just change the code and hope it works. Everything will be off and the coroutines won't continue. Since Tir uses tiny processes, it's easier to do these upgrades in one part without killing the other parts, and since users are never in any one process for very long by design the risk is smaller. But, you definitely have to be more careful than the other models.