Lakehouse Research Base

Jan 20, 2026 · Databases

Why Is Your Elasticsearch Cluster Yellow? 5 Causes & Fixes for Unassigned Replicas

This guide walks through a systematic troubleshooting process for Elasticsearch yellow cluster status, covering how to diagnose unassigned replica shards using cluster health, shard allocation, and allocation explain APIs, then resolves the five most common causes: insufficient nodes, disk watermarks, disabled allocation, node failures, and oversized shards, with commands for both curl and Kibana Dev Tools.