As @wernerb already pointed out, the idea is to use context.become such that inside your actor the only side-effects happening are due to context.become, otherw

As @wernerb already pointed out, the idea is to use context.become such that inside your actor the only side-effects happening are due to context.become, otherwise the data structures are left immutable, the helper functions are left pure, etc... and it becomes easier (less error prone) to manage complex actors that way. Another side-effect of this for example is that you're not going to worry about vars that leak into Future computations, which is a mistake that even experienced developers are doing, because it's an easy one to make. Here's your sample translated into a state-machine with 2 states: https://gist.github.com/alexandru/63eebe8e49e796f31e73 https://gist.github.com/alexandru/63eebe8e49e796f31e73