Hey Ivan,
If you believe you've run into an issue on the platform, the best place to post is the
Public Issue Tracker. As it stands, we'll be happy to look into your app regardless, but it's good to know the right forum for future posts, anyhow. One possible explanation for this is that you didn't exceed the daily quote but a rate-limiting quota defined over a smaller time-frame. Providing not just your project ID but some information about how you're using the datastore, information / estimation about how often you make calls, the theoretical upper bound on how often you could make calls if your app were under heavy use, etc. will greatly speed up our ability to diagnose what's happening and, if necessary, implement a fix.
Cheers!
Nick
Cloud Platform Community Support