Firebase database bandwidth usage growing rapidly

Update: After 9 months of back-and-forth emails (over 40 emails), Google has acknowledged that they have found some bugs that may be responsible for high bandwidth usage, but bandwidth usage is still too high. Resolving this issue does no appear to be a priority for Google/Firebase (it took them 1.5 months to respond to the last email). In light of similar complaints such as: https://news.ycombinator.com/item?id=14356409, and many others, across a wide range of teams/developers, hopefully the situation will improve some day.

I'm just starting a Firebase project and have not accessed the database from any client. I have only created a single tiny test key-value pair in the database (using the console), which uses 23 B of data storage. Surprisingly, the console shows that I have used 215.9 KB (including when I was not touching Firebase at all). This number continues to grow every hour even though I am not using Firebase or even refreshing the data tab in the console!

Here is a screenshot of the console bandwidth usage chart: Firebase console bandwidth usage screenshot

Others appear to be having the same problem, but there has been no response from Firebase/Google. What's going on? Any help would be greatly appreciated.

The usage chart takes time to update. You may be seeing bandwidth from a few minutes to a few hours ago.

Also, this reminds me of the old Google Analytics referrer issue, the default rules for firebase look something like this:

.read = true;
.write if auth != null;

This means that anyone anywhere can read from your database and that anyone authenticated(even anonymously) can write to it. It is possible since it is a noSQL database with json support that it is probably just crawlers which are the equivalent of Google Analytics referral spam.