Cloud Functions for Firebase - Billing account not configured
Make sure that your project is linked to a billing account.
If you navigate to https://console.cloud.google.com/billing
You should be able to find your Firebase project listed there. If not, then you will need to go to the list of projects, and from your projects menu, select billing then link a billing account to it.
The "Billing account not configured" warning message is automatically logged by Google Cloud Functions when no billing account is configured. It doesn't mean that your code isn't working, but it merely there as a reminder just in case you have a problem.
The restriction is about outbound access - e.g. can your Function request resources from the general internet. Its absolutely fine to use a function to respond to a webhook, or to access Google-internal services such a the Realtime Database.
If you wanted to call a third party web service (for example) you'd need to enable billing.
For the other quotas, take a look at: https://firebase.google.com/pricing/ - as you can see there are limits to the number of invocations (125,000 at time of writing) and CPU and memory (40k cpu-seconds and 40k GB-seconds) in the free tier.
Doug stevenson's answers helped me best:
TL;DR: It's a warning message. if you are not doing outbound calls, you are fine
That warning message appears for all functions when executing on the Spark plan. It's just a warning - you can ignore it if you're doing doing any outbound networking in your own own.
We're looking into getting that message changed or removed so that it's less confusing.
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