* Add item ID to the workqueue instead

Signed-off-by: Kevin Su <pingsutw@apache.org>

* nit

Signed-off-by: Kevin Su <pingsutw@apache.org>

* Update the item only if it exists in the cache

Signed-off-by: Kevin Su <pingsutw@apache.org>

* Update tests

Signed-off-by: Kevin Su <pingsutw@apache.org>

* nit

Signed-off-by: Kevin Su <pingsutw@apache.org>

* address comment

Signed-off-by: Kevin Su <pingsutw@apache.org>

* fixed tests

Signed-off-by: Kevin Su <pingsutw@apache.org>

* address comment

Signed-off-by: Kevin Su <pingsutw@apache.org>

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Signed-off-by: Kevin Su <pingsutw@apache.org>