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An alternative strategy is to implement it so that stickiness take precedence and all previously assigned partitions are preserved; while the new consumers or partitions that need to be assigned do so towards the fairest possible assignment. We may call this alternative the sticky yet fair or fairest sticky strategy. This strategy would be more efficient as it exhibits less complexity and variance. After all, the previous valid assignments remain as they are and only a few new assignments have to be calculated.

The fair strategy discussed in KIP-49 considers fairness only and does not take into consideration the partition assignments before the rebalance. Fairness only can also be supported as part of this KIP by switching off stickiness and always starting from an empty currentAssignment.

Compatibility, Deprecation, and Migration Plan

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