Is Firebase paid or free?

Firebase offers a no-cost tier pricing plan for all its products . For some products, usage continues at no cost no matter your level of use. For other products, if you need high levels of use, you’ll need to switch your project to a paid-tier pricing plan. Learn more about Firebase pricing plans.

Firebase Realtime Database is fairly expensive ($5/GB of storage per month), so it makes economic sense for developers to migrate to their own backend once they hit a certain scale.

All limits and pricing indicated on the Firebase pricing page apply to each separate project . So in your example neither project would be exceeding the limits of its free plan.