Distributed search

Searching an index requires Elasticsearch to query a set of shards that contain all your data. Since shards are distributed across multiple nodes, this query will be forwarded to multiple nodes.

Search process

1. When you make a search request, the node that receives it forwards it to a set of shards that contain all your data. These can be either primary shards or replicas, and are chosen in a round-robin fashion.
2. Then, the coordinator node gathers the results from those shards, aggregates and sorts them, and sends the results back to the client.

Elasticsearch divides each index into shards, which are standalone Lucene indices. These can be either primary shards or replicas. 

The number of shards and replicas per shard is set when a new index is created. After that, Elasticsearch takes care of evenly distrib...