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1. For us to guarantee ordering, childThread's records cannot be returned until parentThread has finished processing theirs. So until parentThread finishes processing offsets 1-50, the results for childThread will have to be stored temporarily. 
2. Each time a call for more metadata is made, childThread's results will be sent to to a PriorityQueue monitored by parentThread via callback. But they will not be sent to the client until all offsets before it has been sent to the client.
3. At some point, offsets 1-50 has been returned. In this case, we will return childThread's records as well if another metadataForStore method call was made. So basically, we are delaying the sending of records processed by childThread until the offsets before it has been received by the user.

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