It can increase latency (which can be somewhat mitigated though by having a write buffer e.g. on EBS volumes), but it substantially _reduces_ cost: all cross-AZ traffic (which is $$$) is handled by the object storage layer, where it doesn't get charged. This architecture has been tremendously popular recently, championed by Warpstream and also available by Confluent (Freight clusters), AutoMQ, BufStream, etc. The KIP mentioned in the post aims at bringing this back into the upstream open-source Kafka project.