THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
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3. v3 of the record format should make it cheaper to make changes in the future (perhaps it could support tagged fields or similar)
4. We'd want to fix other known issues at the same time (eg log append time should always be available, there may be others)
5. We should consider whether we would want to introduce a user header that is at the batch level vs record level for efficiency reasons
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