I don't have an application to submit at the moment, but can I apply the key first?
Don't register for a key until you need it.
See "How API Keys Work" for more about API keys.
You don't need an API key until your app goes live. For small traffic amounts (under 300 requests/day) you can use the API without the key to test your app:
Do I need an API key?
A single IP can only make a limited number of requests per day to the API. This limit is determined at first request time, and is dependent upon the presence of an API key.
API daily limits:
No Key: 300
No Keylimit is meant to facilitate experimentation, not for deployed apps.
Requests with invalid or revoked keys are not completed, they are not stepped down to the
No Key limit.