Google Simple API key stopped working

Question

I'm using Python/Twisted to do asynchronous HTTP calls to the Google+ API. Our client app passes over the user's access_token and we do an API call to...

https://www.googleapis.com/plus/v1/people/me/?%s&key=%s&

... where %s and %s are being filled with a valid access_token and (supposedly) valid Simple API Key, respectively.

Everything was working beautifully yesterday. Today I continued to work on the unit tests for this when the API suddenly started returning:

{
 "error": {
  "errors": [
   {
    "domain": "usageLimits",
    "reason": "keyInvalid",
    "message": "Bad Request"
   }
  ],
  "code": 400,
  "message": "Bad Request"
 }
}

usageLimits, keyInvalid... Okay, I get it. I've seemingly hit the usage limits and they have invalidated API keys coming from this account. Except, I haven't...

The "Courtesy Limit" is supposed to be "10,000 requests/day", yet I've only made a couple hundred calls (according to Google's own usage graphs), and I am still seeing "0% used" on the quotas tab.

I would have brought this to Google directly, but they seem to have dropped their Developers Google Group in favor of a Google+ discussion that doesn't actually receive any responses.

Any help or guidance is extremely appreciated. Thanks!

Answer 1

The answer was quite simple! You can't send both the access_token and the key in the same API call. If you use the access_token you're authenticating the API call as the user, if you use your projects Simple API Key you're authenticating as yourself. If you use both, the call fails.