3 lessons learned from an Elasticsearch game day

The article details how to troubleshoot and resolve "unassigned shards" in Elasticsearch, which occur when shards can't be allocated to nodes. These unassigned shards can stem from node failures, insufficient resources, or configuration issues like shard allocation filtering. The solution involves identifying the root cause (using cluster health and allocation explain APIs) and then taking corrective actions like adding nodes, increasing resources, or adjusting shard allocation settings to allow Elasticsearch to rebalance and assign the missing shards.