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The above bootstrapping process might take some time to finish, for the use cases which are sensitive to time delay the user might want to configure one or more follower brokers as a hot standby.  Alternatively as an a future enhancement of this KIP, we can optimize the bootstrap time of the new leader by having it sync with the object storage on the last few seconds of the data when it becomes the new leader (and sync the rest of the data slowly async in the background).  In a well operated Kafka pipeline, the consumer is usually only behind on the tail of the Kafka queue by a few seconds, once the new leaders get these few seconds of data from object storage the consumer can resume the consumption flow.

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For acks=-1 producer path, there is a slight extra delay because data is transferred onto object storage first before it is downloaded onto the follower broker.  This delay can be reduced by tuning the batch size of the upload.  And for some use cases, the user might decide be able to treat data synced to object storage as acks=-1 completed since the data on object storage is multi-way replicated already.  For this as a future enhancement we can add a mode to acknowledge back to the producer as soon as the data is uploaded onto object storage.  This would give us the same performance with current Kafka implementation.  The extra work we would need to do to complete this mode is to have the new leader (elected from the follower broker during leadership change) to pause and catch up with the object storage when it becomes the new leader.  ..

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