Hi there,
Can you clarify a bit what you need ERPNext to do? When you say that “usage is posted to the subscription as it happens”, what does that mean specifically? How is usage being tracked, and which service is responsible for tabulating and invoicing?
Frappe has excellent integration interfaces, so the answer to your question is almost certainly “yes”, but we’ll need a bit more detail about the workflow to answer more specifically. I’m only loosely familiar with Stripe, and a quick google search didn’t turn up much for usage-based subscriptions.