We hit that HTTP request limit as well, and (driven by a discussion with Google support) migrated our backend away from the REST-based Google Cloud Datastore AP

We hit that HTTP request limit as well, and (driven by a discussion with Google support) migrated our backend away from the REST-based Google Cloud Datastore API to the internal (ApiProxy-based) Appengine API. Reduced the latency as well. I can send you the internal support ticket nr if interested.