My question is basically as stated in the title. I am examining using Firebase for our app backend (and an accompanying Nodejs server to take care of a couple of things that Firebase can't handle since it doesn't support Webhooks). I have an expectation that our database will contain millions of records - tens of thousands of users, thousands of a specific entity type and tens of thousands of records per each of those entities. While I do think the data can be flattened to simpify and speed queries, I am worried that Firebase is really not designed for a datastore of that size.
Does anyone have experience with huge datastores in Firebase and can offer some insight here?