I am trying to run Parse Server, a Node.js app, on Google App Engine. And I am on trial period with $300 free credit.
From this page, https://cloud.google.com/appengine/docs/quotas, it says there is 28 free instance-hours per day. The app is running with 2 instances and, according to the report, my account is being charged for Compute Engine (G1 Small) for 48 hours everyday.
So how could I benefit from that 28 free hours?
There are 28 free instance-hours per day for frontend instances only when you are using one of the standard environments or runtimes(python, java, php and go) and not when you're using app engine's managed VMs. All managed VM environments are based on Compute Engine and are all billable.
For a nodejs app, you're certainly using a managed VM.
To enjoy the free instance hours you'll need to use one of the standard runtimes.
来源：https://stackoverflow.com/questions/35589951/how-to-run-app-on-app-engine-for-free