The google cloud datastore server fails

The google cloud datastore server fails

This worked well, but now fails me. Maybe is an error because it's a beta.
POST
https://www.googleapis.com/datastore/v1beta1/datasets/gaep81me/beginTransaction?key={YOUR_API_KEY}
Content-Type: application/json
Authorization: Bearer ya29.AHES6ZRouAaPjnnEuWGc0jjVtisvb08ZD9qKUajtIj_7N7qT
X-JavaScript-User-Agent: Google APIs Explorer
{
"isolationLevel": "serializable"
}
"gaep81me" is a correct ID. I've tried with a lot of projects ID; and in
diferent accounts. And using each account for their projects.
The token is correct: was produced by the Api explorer
https://developers.google.com/apis-explorer/#p/datastore/v1beta1/datastore.datasets.beginTransaction
including the scopes www.googleapis.com/auth/userinfo.email and
www.googleapis.com/auth/datastore
I receive this
503 Service Unavailable
... (headers)...
{
"error": {
"errors": [
{
"domain": "global",
"reason": "backendError",
"message": "Backend Error"
}
],
"code": 503,
"message": "Backend Error"
}
}
My python application (using auth2 + json api) fails too... is not a
problem with the Api explorer page. I think that datastore is down. An
status page for cloud datastore will be fine. Another good thing is to
rename this service to distinguish it from the appengine version. Thanks.