Elasticsearch tips: auto_expand_replicas

📅 Published: Apr 10, 2025 • Thomas Queste

The auto_expand_replicas setting in Elasticsearch dynamically adjust replica counts during cluster scaling.

TL;DR

The auto_expand_replicas setting automatically adjusts replica count when nodes change
Eliminates manual replica management during cluster scaling
Set to 0-all for replicas on all available data nodes
Use custom ranges like 0-2 for controlled replication

Auto-expand replicas solves this by dynamically adjusting replicas based on cluster size.

⭐ We use this in our performance environment after scaling operations to get the appropriate number of replicas.

Because it happened, we forgot to increase the number of replicas after scaling up the cluster! 😫

PUT my_index
{
  "settings": {
    "auto_expand_replicas": "0-all"
  }
}