Elasticsearch Interview Questions and Answers

Ques 41. How does Elasticsearch achieve high availability?

Elasticsearch achieves high availability through the concept of replication. Each shard has one or more replicas, and if a node fails, its shards can be served by replicas on other nodes.

Example:

PUT /my_index/_settings
{
  "number_of_replicas": 2
}

Ques 42. How can you improve the performance of Elasticsearch queries?

Performance can be improved by optimizing mappings, using proper analyzers, and scaling the cluster horizontally.

Ques 43. What is the purpose of the 'Query DSL' in Elasticsearch?

The Query DSL (Domain Specific Language) in Elasticsearch is used to define queries in a JSON format. It allows for complex and flexible querying of data.

Example:

{
  "query": {
    "match": {
      "field": "value"
    }
  }
}

Ques 44. What is the purpose of the 'Fielddata' cache in Elasticsearch?

Fielddata cache stores the data structures necessary for sorting and aggregating on fields, improving performance.

Ques 45. Explain the 'Bulk' API in Elasticsearch.

The Bulk API in Elasticsearch allows you to index, delete, or update multiple documents in a single request for better performance. It reduces the overhead of handling individual requests.

Example:

POST /my_index/_bulk
{ "index": { "_id": "1" } }
{ "field": "value1" }
{ "delete": { "_id": "2" } }
{ "create": { "_id": "3" } }
{ "field": "value3" }