Scale OpenSearch shards online without spiking search latency

A runbook for fixing hot shards with controlled migration, aliases, parity checks, and a clean rollback path.

Learn how to diagnose hot shards, decide whether primary shard scaling is justified, and run an online OpenSearch migration without losing writes or breaking searches.

Created: August 19, 2026

Published: August 19, 2026

Estimated time45 min

LevelAdvanced

Before you startRead access to OpenSearch Dev Tools or curl against the cluster API

PlatformsLinux / Docker

WhatsApp X LinkedIn

Linux

Diagnose and migrate from a terminal with curl, jq, and before/after metric snapshots.

curljqTLS/API access to the OpenSearch cluster

Inspect current shard layout

curl -s "$OS/_cat/shards/logs-prod-2026.08?v&h=index,shard,prirep,state,docs,store,node"

Inspect active migration tasks

curl -s "$OS/_tasks?actions=*reindex&detailed=true" | jq .

Atomic alias cutover

curl -s -XPOST "$OS/_aliases" -H "content-type: application/json" -d @alias-cutover.json

Also available inEscalar shards online en OpenSearch sin disparar la latencia de búsqueda

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