Our Firebase bill has been 10x what we predicted, we didn’t know why but your article describes the probably cause.

What we replaced Firebase with, which is awesome, is:

• a virtual server at Vultr, $40/month for 8 GB RAM, 100GB SSD storage, and 4 CPUs (half price from most other vendors)
• Elasticsearch for a database (understatement of the year: more powerful and faster queries than Firebase :) )
• Hapi for an API + Nes for real time socket communication with the browser (we found Hapi + Nes easier to set up than Firebase)

I’d be happy to provide any more info or even help you set up a server, would take about 30 min.