1. How do we distinguish between an insert and an update in our insert method?
Check to see if the item to be inserted is already in the datastore
Pass in an optional boolean flag to the insert method

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2. Why did we use an ID on a grade entry?
So that each student can only have one grade entry
Because every object needs an ID

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3. What is the difference between an ID and an entity group?
IDs are globally unique, while entityKeys are only unique within an entity group
Entity keys are globally unique, while IDs are only unique within an entity group

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