It depends. Some state needs to live, some needs to go. Long-lived processes should ideally do few state manipulations, or be easy to replace (so they store les

It depends. Some state needs to live, some needs to go. Long-lived processes should ideally do few state manipulations, or be easy to replace (so they store less state). Risky or frequent operations should be done far down in the supervision tree. The processes with complex state, things that can't be lost, might tend to be long-lived. In these cases, they should either only do very simple operations, or be isolated from the operations on that state. These processes will generally live higher up in the supervision tree structure and delegate the risky work to processes lower in the hierarchy; these short-lived workers will thus have their impact limited, but will also have their state known before some unit of work, a bit like an invariant. If the short-lived worker dies, then restarting it with its short-lived state is a cheap operation. Restarting the long-lived process is a difficult thing because the state might be a) possible to re-compute, but complex to do so, or b) bound to events that cannot be repeated, and can't be lost.