How does app engine charge me when I have a Firebase-queue only listening to Firebase database for changes?

[Sepehr Tahmasebi]

I am trying to understand how the app engine charges me when I have a node.js Firebase-queue instance listening to my database ? Am I being charged for it and if yes for what exactly? 

Thanks

[Adam (Cloud Platform Support)]

Is your Firebase Queue instance running on the App Engine NodeJS runtime? If yes, it's getting charged according to the amount of resources the instances use (CPU, network, disk), the same as any other app running on App Engine. NodeJS currently runs on the flexible runtime, so as mentioned it the previously linked doc it currently is priced according to Google Compute Engine.