--- title: "Apache Kafka Replica Followers: Synchronous or Asynchronous?" url: https://daily.dev/posts/apache-kafka-replica-followers-synchronous-or-asynchronous--hnvn4k0ak source_url: https://softwaremill.com/apache-kafka-replica-followers-synchronous-or-asynchronous type: article source: "SoftwareMill" published: 2026-06-19T12:13:57.389Z updated: 2026-06-20T00:19:52.807Z tags: ["distributed-systems", "apache-kafka", "confluent-cloud"] reading_time: 9 upvotes: 4 comments: 0 language: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Apache Kafka Replica Followers: Synchronous or Asynchronous? **[SoftwareMill](https://daily.dev/sources/softwaremill)** · 9 min read · 4 upvotes · 0 comments ## Summary Apache Kafka follower replicas are often described as both synchronous and asynchronous, causing confusion. The distinction lies in two separate questions: how replication physically works (pull-based, followers can lag — asynchronous) versus when a write is considered committed (ISR followers must acknowledge before acks=all succeeds — synchronous). In Confluent Platform Multi-Region Clusters, this distinction is made explicit: normal replicas in the ISR are synchronous replicas, while observers are asynchronous replicas that don't participate in the ISR-based acknowledgement path. The min.insync.replicas configuration controls the minimum ISR size required for a write to succeed with acks=all, making it critical for durability guarantees in stretched and 2.5 DC architectures. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Similar posts on daily.dev - [Understanding in-sync replicas and replication factor in Confluent Stretched Cluster 2.5](https://daily.dev/posts/understanding-in-sync-replicas-and-replication-factor-in-confluent-stretched-cluster-2-5-ssa0wwvwh) · SoftwareMill · 1 upvotes · 0 comments - [Guide to Apache Kafka Disaster Recovery and Multi-Region Architectures](https://daily.dev/posts/guide-to-apache-kafka-disaster-recovery-and-multi-region-architectures-oc2uf6xpm) · SoftwareMill · 0 upvotes · 0 comments --- Tags: [#distributed-systems](https://daily.dev/tags/distributed-systems), [#apache-kafka](https://daily.dev/tags/apache-kafka), [#confluent-cloud](https://daily.dev/tags/confluent-cloud) [View this post on daily.dev](https://daily.dev/posts/apache-kafka-replica-followers-synchronous-or-asynchronous--hnvn4k0ak)