THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
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Produce and fetch requests with v0 and v1 message formats would be supported via up-conversion and down-conversion. Up-conversion and (especially) down-conversion have measurable performance impact due to the increased CPU and memory usage, but the vast majority of Kafka clients have supported v2 for some time (even Spark, a notable late adopter, has supported v2 since Spark 2.4, which was released in October 2018).
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