Interview Questions and Answers

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

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

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

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

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

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

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 }
        }
      }
    }
  }
}

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
}

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"
      }
    }
  }
}

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
  }
}

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"
  }
}

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"
    }
  }
}

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"
      }
    }
  }
}