Google App Engine Always On feature

Can someone explain what is the Always on feature in Google App Engine ? How is it useful? An explanation with example 开发者_StackOverflow社区will be appreciated.

Does Always on feature work even for task queues?

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Basically, Google shuts down app engine app instances when they have no traffic. With this feature, you can pay extra to have an instance always running. This saves time during traffic spikes as time does not need to be taken to launch a new instance.