Elasticsearch Interview Questions and Answers

Ques 1. How does Elasticsearch handle security?

Elasticsearch provides security features like role-based access control, SSL/TLS encryption, and authentication mechanisms.

Ques 2. 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 3. How does Elasticsearch handle conflicts during distributed writes?

Elasticsearch uses versioning to handle conflicts during distributed writes, ensuring data consistency.

Ques 4. How can you handle high availability in Elasticsearch?

High availability can be achieved by configuring multiple nodes, using replicas, and implementing proper failover mechanisms.

Ques 5. Describe the 'Scripting' feature in Elasticsearch.

Scripting allows users to write custom scripts for advanced calculations, filtering, and scoring in Elasticsearch queries.

Ques 6. How does Elasticsearch handle conflicts during index updates?

Elasticsearch uses a versioning mechanism to handle conflicts during index updates and ensure consistency.

Ques 7. What is the role of a filter in Elasticsearch?

Filters in Elasticsearch are used to narrow down the search results based on specific criteria. They are applied to queries to exclude or include documents in the search.

Example:

GET /my_index/_search
{
  "query": {
    "bool": {
      "filter": {
        "range": {
          "price": { "gte": 20 }
        }
      }
    }
  }
}

Ques 8. 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 9. What is the purpose of the 'Aggregations' framework in Elasticsearch?

Aggregations in Elasticsearch provide the ability to perform data analysis on the results of a query. They enable you to extract and process aggregated information from the data.

Example:

GET /my_index/_search
{
  "aggs": {
    "average_price": {
      "avg": {
        "field": "price"
      }
    }
  }
}

Ques 10. How can you secure communication in Elasticsearch?

Communication in Elasticsearch can be secured using HTTPS. You can enable SSL/TLS to encrypt the data transmitted between nodes and clients for secure communication.

Example:

PUT /_cluster/settings
{
  "persistent": {
    "xpack.security.http.ssl.enabled": true
  }
}

Ques 11. Explain the purpose of the 'Reindex' API in Elasticsearch.

The 'Reindex' API is used to copy documents from one index to another. It is useful for reorganizing data, changing mappings, or upgrading Elasticsearch versions.

Example:

POST _reindex
{
  "source": {
    "index": "old_index"
  },
  "dest": {
    "index": "new_index"
  }
}

Ques 12. Explain the purpose of the 'Percolator' in Elasticsearch.

The 'Percolator' in Elasticsearch is used for reverse searching. Instead of searching for documents, it allows you to register queries and match them against incoming documents.

Example:

PUT /my_index/_doc/my_percolator_query
{
  "query": {
    "match": {
      "field": "value"
    }
  }
}

Ques 13. What is the purpose of the 'Script' query in Elasticsearch?

The 'Script' query allows you to execute custom scripts during the search process. It is useful for complex calculations or custom scoring logic.

Example:

GET /my_index/_search
{
  "query": {
    "script": {
      "script": {
        "source": "doc['field'].value > 10"
      }
    }
  }
}