In their notifications about the new billing system for the Google Maps APIs, Google very clearly state that you "can set usage limits to protect against unexpected increases". However, I haven't found any documentation regarding how to set these usage limits against an API key. Does anyone know how to do this?
To clarify, I would like to set my own daily usage limits against my API key to prevent it ever going over the free threshold for the static maps API.
I understand Google means that you can set your custom daily quota for each individual API in order to stay within free 200$, not a global per API key/project/Billing account daily quota. As far as I know there is no such thing as limit per daily usage in $ per Billing account yet.
There are alerts that you can establish in your Billing account and receive notifications if your usage is close to the defined budget. Have a look at the following document that explain how to set alerts:
https://cloud.google.com/billing/docs/how-to/budgets?hl=en
If your project uses only Static Maps API, it is easy to set daily quota to stay within 200$ per month. The price sheet says that you can have up to 100 000 free requests per month. That means 100 000 / 31 = 3225
free requests per day. You can go to Quota section of Static Maps API in your project
https://console.developers.google.com/google/maps-apis/apis/static-maps-backend.googleapis.com/quotas?project=YOUR_PROJECT_ID&duration=PT1H
and change your daily quota as shown in my screenshots
edit number requests per day
and you are set.
I hope this helps!