AppEngine: scheduled tasks per Application or per Application Instance?

Question

From what I gather, AppEngine fires up "Application Instances" (for a lack of better terminology that I know of) as a function of demand on the said application.

Now, let's say I define Scheduled Tasks for my Application, is it possible that the said tasks might end-up being run by multiple Application Instances?

The reason I am asking: if my application uses the datastore as some sort of "Task Repository" and I use Scheduled Tasks to pull work items from it, is it possible that an Application Instance might get the same work items as another (assuming I am not adding addition state to account for this possibility) ?

Answer 1

The contract for the Task Queue API is such that it is possible for tasks to be executed more than once - though such occurrences are rare, and they wouldn't result in the same task being executed multiple times simultaneously. If re-execution does occur, it's entirely possible that they'll be executed on different instances.