A search in our support system shows that it depends on your architecture and must be handled at your end by being aware of how the single instance restart can be done by not affecting the other
Below information may or may not help you as it totally depends on your architecture
Generally for pega cloud clients we go with rolling restart from GOC only. from GOC it first completes all non marketing tiers and then will start app nodes
if we have to manually do → then we follow → stream->util->dds->dataflow->adm->vbd->decisionhub->app
STOPPING :Do it in following order:
SMS >> Email >> AppTier >> DecisionHub >> Dataflow >> VBD