The new Google App Engine SDK 4.1 offers a number of new features. For example, it now includes a Channel API, a bi-directional communication service that lets apps push notifications to users. It also adds an “Always-On” feature that allows developers to reserve up to three instances of their applications, so that they remain available at peak load times.
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Other changes to the SDK include the use of Warm Up Requests whenever possible, the lifting of the 30-second limit for background work, and larger API call size limits.
