When you publish live apps through Voiceflow (currently for Alexa and Google only), your apps are automatically added to Voiceflow's hosting services so that you don't have to worry about the underlying hosting setup. On Enterprise plans, can export your code using Voiceflow's SDK to host on your own servers.
When Voiceflow hosts your app, we are counting the utterances all your apps receive over 30 days in aggregate (combined). If your apps receive over 10,000 utterances in aggregate, you will need to upgrade to a higher plan to unlock additional hosting. Every 30 days, your hosting count of free utterances will reset.
We will be rolling out separate, cheaper plans for hosting in future that will be per-app (lots to work on to do this right). However, currently all hosting above 10,000 utterances per 30 days requires a PRO plan.